JPH0218264Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to a muffler, and particularly to a muffler for an internal combustion engine.

(Prior art) For example, the one shown in Figure 2 is known as a conventional silencer. (published by the Society).

In FIG. 2, 1 is an outer cylinder whose both ends are closed by closing plates 2 and 3, and inside the outer cylinder 1 is a partition plate 4,
5 defines U-turn type expansion chambers 6, 7 and a resonance chamber 8 sequentially from the closing plate 2 side. Also,
Reference numeral 9 denotes an exhaust inlet pipe that communicates with the engine via an exhaust manifold (not shown), and the exhaust inlet pipe 9 passes through the expansion chamber 6 and opens into the expansion chamber 7. Further, reference numeral 10 denotes an exhaust outlet pipe 10 that opens to the atmosphere, and the exhaust outlet pipe 10 penetrates the resonance chamber 8 and the expansion chamber 7 to protrude and open into the expansion chamber 6. Also,
The expansion chamber 6 and the expansion chamber 7 communicate with each other through a communication tube 11 fixed to the partition plate 4, and the expansion chamber 7 and the resonance chamber 8 communicate with each other through a cervical canal 12 fixed to the partition plate 5. connected.

In such a silencer, the exhaust gas introduced into the expansion chamber 7 from the exhaust inlet pipe 9 makes a U-turn in the expansion chamber 7, flows from the communication pipe 11 to the expansion chamber 6, and then makes a U-turn in the expansion chamber 6. and is discharged to the atmosphere through the exhaust outlet pipe 10. The noise transmitted from the engine is transmitted through the exhaust inlet pipe 9, the expansion chamber 7 and the communication pipe 11.
and the expansion chamber 6, noise mainly in the medium and high frequency range is reduced,
In the Helmholtz resonator (resonance type muffling element) composed of the cervical canal 12 and the resonance chamber 8, noise in the low frequency region is reduced.

However, in such conventional silencers, the exhaust gas expands twice in the U-turn expansion chambers 6 and 7, then contracts and makes a U-turn before being released into the atmosphere, which causes the engine to become too high. When the engine rotates, the flow rate of exhaust gas increases, and the flow velocity increases, exhaust loss increases and secondary airflow noise increases. As a result, there were problems in that engine output decreased, fuel consumption deteriorated, and exhaust noise increased.

Therefore, in order to solve such problems,
The present applicant previously filed an application for a silencer as shown in FIG. 3 (see Japanese Patent Application No. 58-240569). This muffler includes an outer cylinder 24 that defines a first chamber 21, a second chamber 22, and a third chamber 23 therein, and a first chamber 24 that penetrates through the first chamber 21 and opens into the second chamber 22. An exhaust inlet pipe 25 having a large number of small holes 24A communicating with the chamber 21 and a large number of small holes 24A penetrating the second chamber 22 and the third chamber 23 and opening into the first chamber 21 and communicating with the third chamber 23. The exhaust outlet pipe 26 has a plurality of small holes 26A formed therein, and a communication pipe 27 which communicates the first chamber 21 and the third chamber 23 and has a large number of small holes 27A formed therein which communicates with the second chamber 22. are doing.

Therefore, part of the exhaust gas sent to the exhaust inlet pipe 25 flows into the first chamber 21 through the small hole 25A, and most of the remaining part flows into the second chamber 22. The exhaust gas that has flowed into the second chamber 22 flows into the communication pipe 27 through the small hole 27A, merges with a small amount of exhaust gas introduced into this communication pipe 27 from the first chamber 21, and then flows into the third chamber 22.
Flows into chamber 23. Furthermore, this exhaust gas is
A into the exhaust outlet pipe 26 and into the first chamber 21
It joins with a small amount of exhaust gas that has flowed into the exhaust outlet pipe 26 and is discharged into the atmosphere. Here, a small amount of exhaust gas flowing from the first chamber 21 through the communication pipe 27 and the exhaust outlet pipe 26 is discharged from the second chamber 22 and the third chamber 23 through the small holes 26A and 27A due to the negative pressure effect. In addition to promoting the inflow and reducing the exhaust pressure, the exhaust gas flowing in the pipe radial direction from the small holes 26A and 27A is directed to the downstream side of the exhaust outlet pipe 26, and furthermore, the flow velocity in the pipe is reduced by the rectification effect. Equalize the distribution. Therefore, most of the exhaust gas that passes through the small holes 26A and 27A and flows through the communication pipe 27 and the exhaust outlet pipe 26 has an extremely low exhaust pressure loss, and the generation of turbulent flow is also suppressed. In addition, the exhaust inlet pipe 25, the second chamber 22 and the communication pipe 2
Exhaust noise is mostly muffled in each extended type muffling element, which is comprised of the third chamber 7 and the third chamber 23, respectively. In particular, these effects are noticeable when the engine rotates at high speed and has a large exhaust flow rate.

(Problem) However, in the case of such conventional silencers, if the pipe diameter is set so that the exhaust pressure does not increase when the engine rotates at high speed and the exhaust flow is large, the flow velocity decreases when the engine rotates at low speed and the exhaust flow is small. In addition, the exhaust pressure also falls further below a value that does not cause a problem in terms of engine output loss. On the other hand, at low rotation speeds and small flow rates, the pipe diameter is too large, so the silencing performance deteriorates, and the fundamental order component of the exhaust pulsation shown in the exhaust noise becomes large. As a result, the muffler has a problem in that it is necessary to increase the amount of muffling when the rotation speed is low and the flow rate is small.

(Means for Solving the Problems) This invention was made to solve the above problems, and includes an outer cylinder in which a first chamber, a second chamber, and a third chamber are defined; The second chamber passes through the first chamber.
An exhaust inlet pipe that opens into the chamber and has many small holes that communicate with the first chamber, and an exhaust inlet pipe that opens into the second chamber and opens into the first and third chambers, and a large number of holes that penetrate the second chamber. a first exhaust outlet pipe that penetrates the second and third chambers, opens into the first chamber, and has a large number of small holes formed in a portion that penetrates the third chamber; A control valve is provided downstream of the small hole forming portion of the first exhaust outlet pipe and reduces the passage cross-sectional area of the first exhaust outlet pipe during low rotational engine operation; A second exhaust outlet pipe is provided, which passes through the second chamber and the third chamber, opens into the first chamber, and has a large number of small holes formed in the portion that passes through the third chamber.

(Function) In this device having such a configuration,
When the engine rotates at high speed and has a large exhaust flow rate, the passage area of the outlet pipe is increased to reduce exhaust pressure loss and secondary airflow noise. On the other hand, when the engine is running at low speed and with a small flow rate, the passage area of the outlet pipe is reduced to effectively suppress pulsation noise, which is the main component of exhaust noise, and to increase the amount of silencing.

(Example) Hereinafter, an example of this invention will be described based on the drawings.

FIG. 1 is a diagram showing an embodiment of this invention.

First, to explain the configuration, in the same figure, 31
is an outer cylinder whose both ends are closed by closing plates 32 and 33, and the inside of the outer cylinder 31 is connected to a first chamber 36, a second chamber 37, and a third chamber 38 from the closing plate 32 side by partition plates 34 and 35. It is defined. An exhaust inlet pipe 39 connected to the exhaust manifold of the engine passes through this first chamber 36 and projects into a second chamber 37 and opens.
A large number of small holes 40 are bored in the tube wall of the penetrating portion. Therefore, the exhaust inlet pipe 39 and the second chamber 37
constitutes an expansion type silencing element, and the large number of small holes 40 and the first chamber 36 constitute a porous resonance type silencing element. 41 is a communication pipe that penetrates the second chamber 37, and one end of this communication pipe 41 is connected to the first chamber 36;
The other ends protrude and open into the third chamber 38, respectively. Further, a large number of small holes 42 are bored in the pipe wall of the portion of the communication pipe 41 that penetrates the second chamber 37 . Therefore, this communication pipe 41 and the third chamber 38 constitute an expandable silencing element. On the other hand, 43 is a first exhaust outlet pipe, and this first exhaust outlet pipe 43
passes through the second chamber 37 and the third chamber 38,
Its inlet end opens into the first chamber 36, and its outlet end opens to the atmosphere. Further, a large number of small holes 44 are bored in a portion of the first exhaust outlet pipe 43 that passes through the third chamber 38, and the diameter of the rear end portion 43A is enlarged. 45 is a second exhaust outlet pipe having a smaller diameter than the first exhaust outlet pipe 43, and this second exhaust outlet pipe 45 also passes through the second chamber 37 and the third chamber 38, and its inlet end is connected to the first chamber 36. The outlet end thereof passes through the rear end portion 43A of the first exhaust outlet pipe 43 and opens into the rear end portion 43A. Therefore, within the rear end portion 43A of the first exhaust outlet pipe 43, the outlet end side of the second exhaust outlet pipe 45 is arranged concentrically, forming a double pipe structure. In this case, the sum of the cross-sectional area of the annular space defined by the inner circumferential surface of the rear end portion 43A and the outer circumferential surface of the second exhaust outlet pipe 45 and the cross-sectional area of the second exhaust outlet pipe 45 is the sum of the cross-sectional area of the second exhaust outlet pipe 45. The opening cross-sectional area is set to be optimal for high rotation and large exhaust flow rates. Note that the third exhaust outlet pipe 45
A large number of small holes 46 are bored in the portion penetrating the chamber 38.

Here, 47 is an electromagnetic control valve, and this electromagnetic control valve 47 is a butterfly-type throttle disposed in the passage of the first exhaust outlet pipe 43 downstream of the portion where the small hole 44 of the first exhaust outlet pipe 43 is formed. Valve 48 and link 49
A rod 5 connected to the valve shaft of the throttle valve 48 via
0, a spring 51 which urges the throttle valve 48 to close the passage of the outlet pipe 43 via the rod 50 and link 49, and when energized, attracts the rod 50 against the urging force of the spring 51. It has a solenoid coil 52. Therefore,
When the solenoid coil 52 is energized, the rod 50
is attracted, and the throttle valve 48 opens via the link 49, and the throttle valve 48 is closed by the biasing force of the spring 51 when the power is not applied (when the engine is operating at low speed). Reference numeral 53 denotes a control unit, to which an engine rotational speed signal N from a rotational speed sensor (not shown) is input, and a power supply voltage is supplied from a power supply V. The control unit 53 outputs an activation signal to the solenoid coil 52 when the engine speed exceeds a predetermined value.

Next, the effect will be explained.

First, when the engine is running at high speed and has a large exhaust flow rate, the control unit 53 energizes the solenoid coil 52, the rod 50 is attracted downward in the figure, and the throttle valve 48 is opened. As a result, the first exhaust outlet pipe 4
No. 3 passage is open, and the optimum open passage area is secured at high rotation and large flow rates.

Here, the exhaust inlet pipe 3 is passed through the exhaust manifold.
A part of the large amount of exhaust gas sent to the small hole 40
Most of the remaining water flows into the second chamber 37 through the first chamber 36 . The exhaust gas that has flowed into the second chamber 37 flows into the communication pipe 41 through the small hole 42, merges with a small amount of exhaust gas that has been led into the communication pipe 41 from the first chamber 36, and flows into the third chamber 38. Flow into. 3rd room 3
The exhaust gas that has flowed into the chamber 8 flows into the first and second exhaust outlet pipes 43 and 45 through the small holes 44 and 46, respectively, and these exhaust gases, which are divided into two, are sent from the first chamber 36 to the first and second exhaust outlet pipes. It joins with small amounts of each exhaust gas guided to the pipes 43 and 45, respectively, and further joins within the rear end portion 45A and is discharged to the atmosphere. On the other hand, a small amount of each exhaust gas flowing from the first chamber 36 into the communication pipe 41 and the first and second exhaust outlet pipes 43, 45 becomes a compressed flow in each pipe 41, 43, 45, and the flow velocity increases, and accordingly Each pipe 41, 4
Since the negative pressure inside 3, 45 increases, most of the exhaust gas tends to flow into the small holes 42, 44, 46. In addition, the small amount of exhaust flow directs the flow in the downstream direction with respect to the exhaust gas flowing in the pipe radial direction through the small holes 42, 44, 46, and due to its rectifying action, the flow rate in the pipes 41, 43, 45 increases. Equalize the distribution. Therefore, exhaust pressure loss when the exhaust gas passes through the small holes 42, 44, 46 and flows inside each pipe 41, 43, 45 is suppressed, turbulence is prevented, and secondary air flow noise is suppressed. be done. Moreover, most of the exhaust noise is muffled in each expansion type muffling element formed by the exhaust inlet pipe 39, the second chamber 37, and the communication pipe 41 and the third chamber 38, respectively.

Next, when the engine is at low rotational speed and small flow rate,
The control unit 53 is the solenoid coil 5
2, and the throttle valve 48 is turned off by the spring 51.
The valve is closed due to the urging force of. As a result, the passage of the first exhaust outlet pipe 43 is closed, so that only the second exhaust outlet pipe 45 is open to the atmosphere. Therefore, the ratio of the opening cross-sectional area of the first and second exhaust outlet pipes 43 and 45 to the cross-sectional area of the first chamber 36 and the third
First and second exhaust outlet pipes 4 relative to the cross-sectional area of the chamber 38
The ratios of the opening cross-sectional areas of the openings 3 and 45 are smaller than those when the throttle valve 48 is open. In other words, compared to the conventional example shown in FIG. 3, this is equivalent to reducing the diameter of the outlet pipe for the first chamber 36 and third chamber 38, which have the same volume as the conventional example.
As a result, exhaust noise can be further reduced,
It is possible to obtain a sufficient silencing effect on the basic order component of exhaust pulsation, which forms the center of exhaust noise when the engine is running at low rotation speed and with a small flow rate. By the way, by closing the first exhaust outlet pipe 43, the second exhaust outlet pipe 4
There is a possibility that the flow velocity of the exhaust gas in the engine 5 increases and the secondary air flow noise increases, but since the exhaust flow rate is small when the engine is running at low rotation speed, the increase in the secondary air flow noise is very small. In addition, the first exhaust outlet pipe 43
By closing the exhaust pressure, it is possible that the exhaust pressure increases and the engine output decreases, but as the exhaust flow rate is small as mentioned above, the absolute value of the exhaust pressure does not increase and the engine output decreases. There's nothing to do. That is, in order to suppress the output loss to 5% or less in an engine with a displacement of 3000 c.c., the inner diameter of the first exhaust outlet pipe 43 should be 60 mm, and the inner diameter of the second exhaust outlet pipe 45 should be 34.9 mm. If both are set, both exhaust outlet pipes 43 and 45 must be opened when the engine speed increases to 4000 rpm or more. However, the engine speed
When the engine speed is 4000 rpm or less, the output loss can be suppressed to within 5% by opening only the second exhaust outlet pipe 45. In this way, even when the engine is running at a low rotation speed and a small flow rate, the amount of silencing can be increased without reducing the output of the engine.

(Effects) As explained above, according to this invention,
When the engine rotates at high speed and has a large exhaust flow rate, exhaust pressure loss and secondary air flow noise can be significantly reduced, and as a result, exhaust noise can be reduced and a reduction in engine output can be prevented. Further, even when the engine is running at a low rotation speed and a small exhaust flow rate, exhaust noise, especially pulsation noise, can be effectively suppressed without reducing the engine output.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing one embodiment of a silencer according to this invention, and FIGS. 2 and 3 are cross-sectional views showing a conventional automobile silencer. 31...Outer cylinder, 36...First chamber, 37...Second
Chamber, 38...Third chamber, 39...Exhaust inlet pipe, 40
... small hole, 44 ... small hole, 43, 45 ... exhaust outlet pipe, 44 ... small hole, 46 ... small hole, 47 ... electromagnetic control valve (control valve).

Claims (1)

[Scope of utility model registration request] An external cylinder having a first chamber, a second chamber, and a third chamber defined therein, and an exhaust gas having a number of small holes penetrating the first chamber and opening into the second chamber and communicating with the first chamber. An inlet pipe, a communication pipe that penetrates the second chamber, opens into the first and third chambers, and has a large number of small holes formed in the part that penetrates the second chamber, and penetrates the second and third chambers. A first exhaust outlet pipe is provided downstream from the small hole forming part of the first exhaust outlet pipe, and has a large number of small holes formed in the part that opens into the first chamber and passes through the third chamber. a control valve that reduces the passage cross-sectional area of the first exhaust outlet pipe during rotational operation; A silencer characterized by comprising: a second exhaust outlet pipe having a large number of small holes formed in a portion penetrating the chamber.