GB2383091A

GB2383091A - Engine silencer for controlling back pressure and gas leakage

Info

Publication number: GB2383091A
Application number: GB0303498A
Authority: GB
Inventors: Jefferson Liu
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-08-18
Filing date: 2000-08-18
Publication date: 2003-06-18
Also published as: CN1454286A; GB0303498D0; AU2000265542A1; WO2002014561A1

Abstract

The present invention relates to an engine silencer for controlling back pressure and gas leakage. The silencer includes an outer tube, an inner tube coaxial through the outer tube, plates with holes disposed at the space between the inner and outer tubes, and convergent tubes spaced located in the inner tube to accelerate the gases into the inner tube and assistant the exhaust valve of the engine. Between opening of exhaust valve and dead of bottom of the piston, the silencer has a high back pressure to resistance the leakage of the gases expanding in the cylinder.

Description

OFFICE - DEFINING COr^ -t 1 MUFFLER 2383091

2 BACKGROUND OF THE INVENTION

3 1. Field of the invention:

4 The present invention relates to a muffler, and more particular to a muffler 5 having an outer tube and an inner tube securely mounted inside the outer tube.

6 The inner tube has multiple through holes defined in a periphery thereof and 7 multiple shrink throats formed therein. Multiple baffles are provided between 8 the outer tube and inner tube and each having multiple holes defined to 9 communicate with spaces defined by the baffles. When the engine is in 10 operation, the discontinuous discharge exhaust air from the engine will fill in the spaces and therefore generates a backpressure, which increases the 12 resistance to the discharge of the exhaust. Before the piston of the engine is 13 reaching the bottom dead center, said backpressure can reduce the power loss 14 due to the early opening of the exhaust valve in the power (expansion) stroke.

15 When the exhaust air passes the shrink throats, the speed of the exhaust air is 16 increased (by the Venturi Tube Theory, PAVE= P2V2). After the exhaust air 17 passes through the first shrink throat, because ofthe increase in the speed of 18 the exhaust air, the air in the first space is sucked in, therefore builds up a 19 pressure before the second shrink throat. As said process goes on, the exhaust 20 function is discharged thoroughly.

21 2. Prior art description:

22 Generally speaking, there are four different strokes in an engine when 23 generating power: intake, compression, expansion and exhaust. When the 24 piston of the engine is moving from the bottom dead center (BDC) to a top

1 dead center (TDC), the engine is processing either the compression stroke or 2 the exhaust stroke. When the piston is moving nearly to the TDC, the intake 3 valve and exhaust valve are closed to start the expansion stroke. The sudden 4 pressure generated by the explosion caused by the sparking plug will push the 5 piston back to the BDC to be ready for the next stroke, the exhaust stroke.

6 However, in order to discharge the exhaust function from the expansion stroke, 7 the exhaust valve will be opening before the piston reaches the BDC. The early 8 opening of the exhaust valve will cause a loss to a portion of the power 9 generated from the expansion stroke. To avoid such situation, the exhaust valve 10 should be opening as late as possible. However, another problem arises should l l the exhaust valve be opening, too late. That is, if the exhaust valve be opening 12 too late, the exhaust function from the expansion stroke will not be able to 13 discharge thoroughly, which will hinder the exhaust stroke to process properly.

14 Consequently, the entire exhaust stroke procedure will be influenced seriously.

15 This dilemma troubles engine designers.

16 It is an objective of the invention to provide an improved muffler to obviate 17 and mitigate the aforementioned problems.

18 SUMMARY OF THE INVENTION

19 The primary objective of the invention is to provide an improved muffler to 20 provide a sufficient backpressure to reduce the power loss in the expansion 2 1 stroke.

22 Another objective of the invention is to increase the speed of the exhaust air 23 to reach the requirement of discharging the exhaust function thoroughly in the 24 exhaust stroke.

1 Other objects, advantages and novel features of the invention will become 2 more apparent from the following detailed description when taken in

3 conjunction with the accompanying drawings.

4 BRIEF DESCRIPTION OF THE DRAWINGS

5 Fig. 1 is a cross sectional view of the muffler constructed in accordance with 6 the present invention; and 7 Fig. 2 is a schematic view showing the operation of the exhaust air in the 8 inner tube of the muffler of the invention; and 9 Fig.3 is a valve timing diagram of the four-stroke engine.

10 DETAILED DESCRIPTION TO THE PREFERRED EMBODIMENT

11 With reference to Fig. 1, a muffler (1) of the invention has an outer tube 12 (11) and an inner tube (12) longitudinally received and confined inside the 13 outer tube (11). The outer tube (11) is mounted outside the inner tube (12) in an 14 air-tight manner. The inner tube (12) has two open ends (not numbered or 15 shown) and one of which is connected with the engine and the other one of the 16 open end communicates with the ambient air.

17 The inner tube (12) has multiple peripherally defined through holes (120) 18 and multiple shrink throats (three are shown in this preferred embodiment of 19 the invention) (121,122,123) each spaced with the other for a predetermined 20 distance. The inner section area of the first shrink throat (121) is the largest of 21 the three and the third shrink throat (123) is the least of the three.

22 Multiple baffles (111) are set between the inner periphery of the outer tube 23 (11) and the outer periphery of the inner tube (12), such that multiple spaces 24 (three are shown in this preferred embodiment of the invention) (112,113,114)

1 are defined between baffles ( 111). Each of the baffles (111) is defined between 2 two adjacent shrink throats; for example the first shrink throat (121) and the 3 second shrink throat (122).

4 When the engine is in operation, referring, to Fig. 2, within seconds, the 5 discontinuous discharged exhaust air from the engine will fill in the spaces 6 ( 112,113,114) and therefore builds a pressure in each of the spaces 7 ( 112,1 13,114). Before the engine continues to operate and the piston of the 8 engine is reaching the BDC (B of fig. 3), the exhaust valve starts to open (D of 9 fig. 3) to proceed to the exhaust function (E of fig. 3). The discharged exhaust 10 air (2) (2 of fig. 2), when reaching the inner tube (12), generates a l 1 backpressure due to the pressure in the spaces (1 12,1 13,1 14) and the first 12 shrink throat (121), which increases the resistance to the discharging of the 13 exhaust air (2) (2 of fig. 2) and picks up its speed in the meantime. However, 14 when the exhaust air (2) continues to proceed to the second shrink throat (122), 15 the exhaust air (2) again picks up its speed. After the exhaust air (2) passes the 16 second shrink throat (122) and moves toward the third shrink throat (123), the 17 speed of the exhaust air (2) is once again increased. This phenomena can be 18 explained by the P V =P2V2 (Venturi Tube Theory). After times of increasing 19 the speed, the exhaust air (2) is discharged quickly.

20 When the piston reaches the TDC (A of fig. 3) and the exhaust valve 21 closes (C of fig. 3), the pressure in the inner tube (12) vanishes quickly, which 22 generates a radial suction to the air in the spaces (112,113,114) through the 23 through holes (120). The radial suction balances the pressure in the inner tube 24 (12), which provides a resistance to the following exhaust from the exhaust

1 stroke so as to reduce the power loss.

2 With the arrangement, when the exhaust air (2) passes the first shrink 3 throat (121), its speed increases. Because ofthe increase in the speed ofthe 4 exhaust, the air in the first space (112) is sucked in, which builds up a pressure 5 before the second shrink throat (122) to further hinder the pointer loss. After 6 the exhaust air passes the second shrink throat (122), the air in the second 7 space (113) is sucked in, which builds up a pressure before the third shrink 8 throat (123). Due to the pressure before the third shrink throat (123), the 9 speed of the exhaust air (2) increases again, which increases the discharging of 10 the exhaust.

11 It can be concluded that the mumer of the invention is able to decrease the power 12 loss from the expansion stroke and increase the efficiencyof the discharging of the 13 exhaust from the exhaust stroke.

14 It is to be understood, however, that even though numerous characteristics 15 and advantages of the present invention have been set forth in the foregoing 16 description, together with details of the structure and function of the invention,

17 the disclosure is illustrative only, and changes may be made in detail, especially

18 in matters of shape, size, and arrangement of parts within the principles of the 19 invention to the full extent indicated by the broad general meaning of the terms 20 in which the appended claims are expressed.

Claims

1 WHAT IS CLAIMED IS

2 1. A muffler comprising: 3 an outer tube; 4 an inner tube sealingly surrounded by and extended out from the outer tube 5 and having multiple shrink throats securely formed therein and multiple 6 through holes peripherally defined therein; and 7 multiple baffles each formed between an inner periphery of the outer tube 8 and an outer periphery of the inner tube and having multiple openings defined 9 therein, wherein a plurality of spaces are defined between the outer tube and 10 the inner tube and each communicates with the multiple through holes of the 11 inner tube; 12 whereby the exhaust air increases its speed after passing through each of 13 the shrink throats in the inner tube so as to increase the efficiency of 14 discharging the exhaust function.

15

2. The muffler as claimed in claim 1, wherein the inner tube has two open 16 ends, one of which is adapted to connect to the engine and the other one to 17 communicate with ambient air.

18

3. The muffler as claimed in claim 2, wherein the shrink throats are 19 configured to have different section areas and are sequentially arranged from 20 the largest one to the smallest one in the inner tube in a descending manner.