GB1578992A

GB1578992A - Muffler

Info

Publication number: GB1578992A
Application number: GB3179279A
Authority: GB
Original assignee: Nihon Radiator Co Ltd
Current assignee: Marelli Corp
Priority date: 1976-08-31
Filing date: 1977-03-18
Publication date: 1980-11-12
Also published as: JPS5333747U; JPS5648893Y2

Description

(54) MUFFLER (71) We, NIHON RADIATOR CO. LTD.

(NIHON RAJIEETA KABUSHIKI KAISHA), of 15 of 24 Minamidai 5-chome, Nakano-ku, Tokyo, Japan, a Japanese Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: - The present invention relates to a muffler, and more particularly to a muffler of the expansion type for use with an engine of an automobile and the like and is divided out of Application No. 11532/77 (Serial No. 1,578,991).

Heretofore, a muffler of the expansion type has been known as a muffler for muffling the exhaust gas of the engine, the pressure of which varies in pulsating manner, wherein the exhaust gas is expanded in the muffler and then the flow of the exhaust gas is contracted in order to muffle the sound.

However, such a prior art muffler of the expansion type has disadvantage that undesired noise will be generated from the outlet pipe of the muffler at the rapid acceleration or the rapid deceleration of the engine, although the muffler exhibits proper muffling effect at the normal driving condition of the engine. Further, the muffler will generate undesired noise depending upon the position of the muffler with respect to the engine, although the first mentioned disadvantages are avoided.

In the prior art muffler of the expansion type, when a throttled portion is formed at an open end of the exhaust gas inlet pipe, a fatal disadvantage for a muffler will be caused that a secondary noise of gas flow is generated from the throttled portion, although the throttled portion exhibits a rough rectification of the pulsation of the exhaust gas in the exhaust gas introducing pipe.

Further, in the prior art muffler of the expansion type, the securing of the exhaust gas conducting pipes to the main body of the muffler could not be made rigid, so that the pipes tended to come off from the mating recesses or the mating cylindrical flanges of the main body of the muffler and, when the pipes are secured to the mating portions by welding, the welding operation was very troublesome, while the welded portions suffered from being broken or the pipes might be jolted or come off from the mating portions due to severe vibration of the main body of the muffler, the thermal expansion of the main body resulting from the passage of high temperature exhaust gas through the muffler or due to the failure of the welded portions in the fixing construction of the pipes.

The present invention aims at avoiding the above mentioned disadvantages and providing a muffler having superior performance.

An object of the present invention is to provide a muffler of the expansion type for the exhaust gas of an engine generating pulsating noise, which can efficiently muffle the noise of the exhaust gas.

Another object of the present invention is to provide a muffler of the expansion type having the above mention characters, while it is simple in construction.

A further object of the present invent tion is to provide a muffler of the expansion type which is simple in construction and which can positively prevent the secondary noise of the gas flow from being generated.

According to the present invention there is provided a muffler. comprising a sealed, essentially-cylindrical main body, an exhaust gas inlet pipe, an exhaust gas outlet pipe, a portion of each of said pipes being disposed within said sealed cylindrical main body, the end of said portion of said exhaust gas inlet pipe within said main body being constricted and open, and a cap member of a foam metal covering said open end.

The invention will be described further by way of example with reference to the accompanying drawings in which: - Fig. 1 is a sectional view showing a muffler, Fig. 2 is a sectional view showing the core of ejected flow of the exhaust gas formed at the throttled open end of the inlet pipe; and Fig. 3 is a perspective view showing the cap body attached to the muffler of Fig. 1.

Fig. 1 and 3 show the muffler in accordance with the present invention, wherein a throttled portion is formed at the open end of an exhaust gas introducing pipe so that the generation of the secondary noise of the gas flow is positively prevented by the simple construction of the muffler.

When the throttled portion is formed at the open end of the exhaust gas introducing pipe, it has the effect that the pulsation of the exhaust gas is roughly rectified in the pipe, but it has also a fatal disvantage for a muffler that secondary noise of the gas flow is generated as described later. Therefore, such a noise must be eliminated.

As shown in Fig 2 when the exhaust gas is ejected from the throttled end 30 of a pipe 2, a jet of exhaust gas is formed consisting of a divergent diffusing gas portion 31 and central conical uniform velocity core portion 32. The diffusing gas portion of the jet generates the secondary noise of the gas flow due to Karman's vortex street and the like. The secondary noise of the gas flow has a property that it is increased as an obstacle 33 having no gas permeability approaches the uniform velocity core 32. The uniform velocity core 32 shows the region in which the flow velocity of the exhaust gas in the pipe 2 is equal to the jet velocity and it is formed in the conical shape having a bottom surface coinciding with the open end of the pipe and a height which is five times the diameter Dl of the open end.

Heretofore, no effective processes have been developed for eliminating the secondary noise of gas flow which is generated when the core is formed in the jet. Thus, the muffling effect of the prior art mufflers has been reduced about by half, even though the open end of the exhaust gas introducing pipe is throttled.

In the embodiment of the present invention, a cap member 34 in generally conical form made of a foamed metal shown in Fig. 3 is put on the throttled open end 30 of the exhaust gas introducing pipe 2, as shown in Fig. 1. The foamed metal is a heat resisting continuous gas permeable body and is made of metallic fibers. The remaining portions of the muffler may be constructed in like manner as in the the case of the respective embodiments disclosed in parent application 11532/77. The numeral 5 designates cylindrical body 6, 7 front and rear end plates, 20 a porous baffle plate dividing the muffler into the front chamber 21 and the rear chamber 22, while 3 designates the exhaust gas discharging pipe passing through the rear chamber 22 and opening in the front chamber 21. The numeral 24 designates the short-circuit holes formed in the exhaust gas introducing pipe 2.

The muffling effect of the embodiment of Fig. 1 will be described below. The pulsation of the exhaust gas flowed into the exhaust gas introducing pipe 2 is roughly rectified in the introducing pipe 2, because the open end 30 is throttled and a portion of the exhaust gas is directly flowed into the rear chamber 22 through the shortcircuit holes 24 so as to prevent the pressure in the introducing pipe 2 from being increased, while the major portion of the exhaust gas flows into the cap body 34 from the open end 30. At this time, since the front portion of the open end 30 is covered by the cap body 34 of the gas permeable continuous porous material, no central core 32 as shown in Fig. 2 is formed and, hence, no secondary noise is generated.Since the cap body 34 is formed in a blind form, the pulsation of the exhaust gas introduced into the cap body is further rectified and the exhaust gas is subjected to the muffling effect, while it passes through the continuous porous material forming the cap body 34 causing repeated expansion and contraction of the flow path and bypass of the exhaust gas, so that the exhaust gas is diffused into the rear chamber 22 in the rectified form from the fine holes in the surface of the cap body 34.

The similar muffling effect is obtained even though the height of the cap body 34 in the conical form is either greater or smaller than the length of 5DI mentioned previously.

As mentioned above, the formation of the core of the exhaust gas jet at the throttled open end can be suppressed, while the exhaust gas is rectified so as to completely prevent the generation of the secondary noise of the gas flow by virtue of the simple construction of the muffler, in which a cap body made of foamed metal is provided, thereby enhancing the muffling effect and exhibiting superior effect in the practical use thereof.

Although the muffler constructed in accordance with the present invention provides a superior muffling effect as mentioned above, the present invention further aims at providing a muffler capable of positively exhibiting the muffling effect as mentioned above.

WHAT WE CLAIM IS:- 1. A muffler, comprising a sealed, essentially-cylindrical main body, an exhaust gas inlet pipe, an exhaust gas outlet pipe,

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. Fig. 2 is a sectional view showing the core of ejected flow of the exhaust gas formed at the throttled open end of the inlet pipe; and Fig. 3 is a perspective view showing the cap body attached to the muffler of Fig. 1. Fig. 1 and 3 show the muffler in accordance with the present invention, wherein a throttled portion is formed at the open end of an exhaust gas introducing pipe so that the generation of the secondary noise of the gas flow is positively prevented by the simple construction of the muffler. When the throttled portion is formed at the open end of the exhaust gas introducing pipe, it has the effect that the pulsation of the exhaust gas is roughly rectified in the pipe, but it has also a fatal disvantage for a muffler that secondary noise of the gas flow is generated as described later. Therefore, such a noise must be eliminated. As shown in Fig 2 when the exhaust gas is ejected from the throttled end 30 of a pipe 2, a jet of exhaust gas is formed consisting of a divergent diffusing gas portion 31 and central conical uniform velocity core portion 32. The diffusing gas portion of the jet generates the secondary noise of the gas flow due to Karman's vortex street and the like. The secondary noise of the gas flow has a property that it is increased as an obstacle 33 having no gas permeability approaches the uniform velocity core 32. The uniform velocity core 32 shows the region in which the flow velocity of the exhaust gas in the pipe 2 is equal to the jet velocity and it is formed in the conical shape having a bottom surface coinciding with the open end of the pipe and a height which is five times the diameter Dl of the open end. Heretofore, no effective processes have been developed for eliminating the secondary noise of gas flow which is generated when the core is formed in the jet. Thus, the muffling effect of the prior art mufflers has been reduced about by half, even though the open end of the exhaust gas introducing pipe is throttled. In the embodiment of the present invention, a cap member 34 in generally conical form made of a foamed metal shown in Fig. 3 is put on the throttled open end 30 of the exhaust gas introducing pipe 2, as shown in Fig. 1. The foamed metal is a heat resisting continuous gas permeable body and is made of metallic fibers. The remaining portions of the muffler may be constructed in like manner as in the the case of the respective embodiments disclosed in parent application 11532/77. The numeral 5 designates cylindrical body 6, 7 front and rear end plates, 20 a porous baffle plate dividing the muffler into the front chamber 21 and the rear chamber 22, while 3 designates the exhaust gas discharging pipe passing through the rear chamber 22 and opening in the front chamber 21. The numeral 24 designates the short-circuit holes formed in the exhaust gas introducing pipe 2. The muffling effect of the embodiment of Fig. 1 will be described below. The pulsation of the exhaust gas flowed into the exhaust gas introducing pipe 2 is roughly rectified in the introducing pipe 2, because the open end 30 is throttled and a portion of the exhaust gas is directly flowed into the rear chamber 22 through the shortcircuit holes 24 so as to prevent the pressure in the introducing pipe 2 from being increased, while the major portion of the exhaust gas flows into the cap body 34 from the open end 30. At this time, since the front portion of the open end 30 is covered by the cap body 34 of the gas permeable continuous porous material, no central core 32 as shown in Fig. 2 is formed and, hence, no secondary noise is generated.Since the cap body 34 is formed in a blind form, the pulsation of the exhaust gas introduced into the cap body is further rectified and the exhaust gas is subjected to the muffling effect, while it passes through the continuous porous material forming the cap body 34 causing repeated expansion and contraction of the flow path and bypass of the exhaust gas, so that the exhaust gas is diffused into the rear chamber 22 in the rectified form from the fine holes in the surface of the cap body 34. The similar muffling effect is obtained even though the height of the cap body 34 in the conical form is either greater or smaller than the length of 5DI mentioned previously. As mentioned above, the formation of the core of the exhaust gas jet at the throttled open end can be suppressed, while the exhaust gas is rectified so as to completely prevent the generation of the secondary noise of the gas flow by virtue of the simple construction of the muffler, in which a cap body made of foamed metal is provided, thereby enhancing the muffling effect and exhibiting superior effect in the practical use thereof. Although the muffler constructed in accordance with the present invention provides a superior muffling effect as mentioned above, the present invention further aims at providing a muffler capable of positively exhibiting the muffling effect as mentioned above. WHAT WE CLAIM IS:-

1. A muffler, comprising a sealed, essentially-cylindrical main body, an exhaust gas inlet pipe, an exhaust gas outlet pipe,

a portion of each of said pipes being disposed within said sealed cylindrical main body, the end of said portion of said exhaust gas inlet pipe within said main body being constricted and open, and a cap member of a foam metal covering said open end.

2. A muffler as claimed in claim 1, comprising a porous partition dividing the interior of said sealed cylindrical main body into a front and a rear chamber and wherein said exhaust gas inlet pipe extends into said rear chamber through said partition, and said exhaust gas outlet pipe communicates with said front chamber through said partition.

3. A muffler as claimed in claim 2 wherein short-circuit holes are provided on that portion of said exhaust gas inlet pipe in said main body.

4. A muffler as claimed in claim 2 in which said cap member is of metallic fiber.

5. A muffler as claimed in claim 1 further comprising a porous partition dividing said main body into a front and a rear chamber, said inlet pipe entering into and communicating with said rear chamber and said outlet pipe communicating with said front chamber, and wherein said inlet pipe has short-circuit holes in that part of the wall thereof within said rear chamber for by-passing a portion of the gas flowing through said inlet pipe into said rear chamber without passing through said cap member.

6. A muffler constructed and arranged to operate substantially as herein described with reference to the accompanying drawings.