CN104213955A

CN104213955A - Dual-mode silencer for internal combustion engine exhausting system

Info

Publication number: CN104213955A
Application number: CN201310217269.0A
Authority: CN
Inventors: 洛朗·马洛潘尼塞
Original assignee: Faurecia Emissions Control Technologies Development Shanghai Co Ltd
Current assignee: Faurecia Emissions Control Technologies Development Shanghai Co Ltd
Priority date: 2013-05-31
Filing date: 2013-05-31
Publication date: 2014-12-17
Also published as: KR20140141416A

Abstract

The invention provides a dual-mode silencer for an internal combustion engine exhausting system. The dual-mode silencer comprises a housing, a first end cover, a second end cover, an input pipe, multiple output pipes and a control device, wherein the first end cover and the second end cover are respectively located at two ends of the housing, the input pipe outward extends from the first end cover so as to collect exhausted gas from an internal combustion engine, the multiple output pipes outward extend from the second end cover, and the multiple output pipes, the input pipe and the housing of the silencer form multiple exhausting paths. The control device is arranged on one of the multiple output pipes and used for operably switching the silencer to be in a first operating mode or a second operating mode according to one or more conditions of the internal combustion engine. The corresponding exhausting path is defined in each operating mode, and at least most of the exhausted gas is transferred through the exhausting paths. The exhausting path corresponding to the first operating path is different from the exhausting path corresponding to the second operating path.

Description

Dual mode muffler for an internal combustion engine exhaust system

Technical Field

The invention relates to a muffler for an exhaust system of an internal combustion engine, wherein the internal combustion engine can be a turbocharged engine or a natural air inlet engine.

Background

In order to reduce the noise generated by the internal combustion engine, a silencer is adopted in an exhaust system. Mufflers typically include a housing, at least one inlet pipe for receiving exhaust gases from the internal combustion engine and at least one outlet pipe for discharging the exhaust gases to the atmosphere. Sometimes, it is desirable to provide two or more exhaust paths to achieve a better tradeoff between acoustic efficiency/backpressure. One of the main problems with internal combustion engines, particularly turbocharged engines, is that the pressure inside the muffler associated with the engine, known as exhaust back pressure, creates resistance to the exhaust gases exiting the engine. The resistance caused by the back pressure adversely affects the performance and efficiency of the internal combustion engine, particularly if the engine is a turbocharged engine.

Therefore, new challenges different from the common development concept of natural induction engines may arise in developing exhaust systems for high performance, high efficiency turbocharged engines. One of these is that the back pressure must be maintained at a level much lower than that of a naturally aspirated engine, not only for high rpm (rmp) conditions (above 6000 rpm), but also for low to medium rpm ranges (between 1000 rpm and 6000 rpm) to ensure the desired performance and efficiency of the turbine engine.

Some designs have used passive "self-actuated" valves to achieve the goal of maintaining a low back pressure in the engine, but this results in a relatively high back pressure at low speeds or mass flow rates. At high rotational speeds, however, the back pressure is kept low by opening the passive "self-actuated" valve as the pressure in the muffler increases. The design solves the back pressure problem at middle and high rotating speed by opening the valve at high pressure in the silencer. However, at low rotational speeds, the valve closes, which generates a high back pressure in the muffler.

While some muffler solutions in current practice use multiple modes in the exhaust system, those modes are arranged in exhaust systems or in mufflers rather than in one muffler. Such a design in multiple exhaust systems or multiple mufflers obviously increases the complexity of the exhaust system and installation problems due to space constraints of the vehicle. Thus, there is a need in the market for a simple, compact muffler solution with the same or better performance and efficiency.

In an example of applying the dual mode muffler to an exhaust system of an automobile, there is an example of reducing the exhaust noise level using two exhaust paths having different muffling efficiencies. In another exemplary embodiment, a bypass is provided to divert a portion of the exhaust gas exiting the muffler at high mass flow rates to relieve back pressure inside the muffler. A pressure-driven passive control valve is used to control the amount of gas that is dispensed. As described above, this design has a high back pressure due to the passive valve closing when the engine is at low speeds.

Us patent 4913260 discloses a device provided to an operator for controlling the reduction of noise generated by airflow in an exhaust system. In this design, since the control signal cannot reflect the rotation speed or exhaust back pressure level in the engine, it cannot be regarded as a scheme of maintaining a low back pressure at a low rotation speed of the engine.

Therefore, there is a need for a muffler solution that has good muffling efficiency at both low and medium and high rotational speeds, while maintaining low back pressure of the internal combustion engine.

Disclosure of Invention

In order to overcome the above problems, the present invention provides a dual-mode muffler for an exhaust system of an internal combustion engine, characterized by comprising: a housing; the first end cover and the second end cover are respectively positioned at two ends of the shell and form a silencer shell together with the shell; an input tube extending outwardly from the first end cap to receive exhaust gases from the internal combustion engine; a plurality of outlet pipes extending outwardly from the second end cap and forming a plurality of exhaust paths with the inlet pipes and the muffler housing; and a control device provided on one of the output pipes for operatively switching the muffler to the first operation mode or the second operation mode depending on one or more conditions of the internal combustion engine. Each operating mode defines a corresponding exhaust gas path through which at least a majority of the exhaust gas is discharged. The exhaust path corresponding to the first operating mode is different from the exhaust path corresponding to the second operating mode.

In a preferred embodiment, the muffler is characterized in that the first operating mode is designed to eliminate noise while maintaining the back pressure below a first preset target value when the internal combustion engine is operating at low speed; a second one of the two operating modes is designed to eliminate noise while maintaining the back pressure below a second preset target value when the internal combustion engine is operating at medium to high speed; the first predetermined target value and the second predetermined target value may be the same value or different values. The first and second preset target values may be defined as preset back pressure values for a given mass flow rate or as other exhaust independent parameter values commonly used in the automotive industry: the Equivalent Section (Equivalent Section) Se, the Loss Coefficient (Loss Coefficient) K or the Nissan alpha Coefficient (Nissan alpha coeffient). For ease of understanding, the relationship between the equivalent cross-section and the back pressure is illustrated by the following example:

<math> <mrow> <mi>dP</mi> <mo>=</mo> <mfrac> <msup> <mi>Q</mi> <mn>2</mn> </msup> <mrow> <msup> <mn>2</mn> <mo>*</mo> </msup> <msup> <mi>ρ</mi> <mo>*</mo> </msup> <msubsup> <mi>Se</mi> <mi>total</mi> <mn>2</mn> </msubsup> </mrow> </mfrac> </mrow> </math>

<math> <mrow> <mi>dP</mi> <mo>≈</mo> <mfrac> <msup> <mn>96</mn> <mn>2</mn> </msup> <mrow> <msup> <mn>2</mn> <mo>*</mo> </msup> <msup> <mn>0.55</mn> <mo>*</mo> </msup> <msup> <mn>5.2</mn> <mn>2</mn> </msup> </mrow> </mfrac> <mo>=</mo> <mn>310</mn> <mi>mbars</mi> </mrow> </math>

wherein:

dP represents the back pressure in mbar, in this case 310 mbar;

q represents the mass flow rate of the engine in g/s;

ρ represents the gas density at a given pressure and temperature, which in this case is 0.55;

se represents an equivalent cross section in cm^2.

The silencer of the invention has high silencing efficiency under low, medium and high frequencies by sharing one sound cavity volume (acousticvolume) under two operation modes. By means of the invention, the silencing efficiency of the engine during speed increasing and speed reducing can be greatly improved, and the volume of the required sound cavity can be reduced.

These and other features of the present invention can be further understood from the following specification and drawings.

Drawings

The invention will be further described with reference to preferred embodiments shown in the drawings and described in detail below.

FIG. 1 shows a schematic perspective view of a muffler according to one embodiment of the present invention.

FIG. 2 is a schematic perspective view of the muffler shown in FIG. 1 with the muffler shell and optional fibers removed.

Fig. 3 is a schematic view of the internal structure of the muffler shown in fig. 1.

Fig. 4 is a schematic view of the exhaust path of the muffler of the present invention operating in a first mode of operation ("pure Helmholtz" mode ").

Fig. 5 shows a comparison of the acoustic efficiency of the muffler of fig. 1 operating in two embodiments of the first mode of operation ("pure helmholtz mode" and "helmholtz with leakage mode").

FIG. 6 is a schematic perspective view of the exhaust path of the muffler of the present invention operating in one embodiment of the first mode of operation ("pure Helmholtz mode").

Fig. 7 is a schematic diagram of an acoustic equivalence (acoustic equivalence) or lumped model (lumped model) of the muffler of the present invention operating in one embodiment of the first mode of operation ("pure helmholtz mode").

Fig. 8 is a schematic view of the exhaust path of the muffler of the present invention operating in a second mode of operation ("jamming (plus absorbing) mode").

Fig. 9 is a graph of the acoustic efficiency of the muffler of the present invention operating in a second mode of operation ("interference (plus absorption) mode").

Fig. 10 is a schematic perspective view of two exhaust paths of the muffler of the present invention operating in a second mode of operation ("jamming (absorbing) mode").

Fig. 11 is an acoustically equivalent schematic diagram of the muffler of the present invention operating in a second mode of operation ("jamming (plus absorbing) mode").

Fig. 12 illustrates the combined acoustic efficiency achieved by the muffler of the present invention.

FIG. 13 is a graphical representation of a binary function of valve position versus control signal (engine speed) in accordance with the present invention.

FIG. 14 is a graphical representation of the valve position versus control signal (engine speed) for the present invention as a linear function.

Detailed Description

Fig. 1 shows an embodiment of a muffler of the present invention. As shown in fig. 1, the muffler 100 has an inlet pipe 101 and two outlet pipes 102 and 103. The inlet pipe 101 provides a connection to the vehicle engine to which the muffler 100 is mounted for receiving exhaust gases. A control device 104 is provided on the exhaust pipe 102. As shown in fig. 1, the housing 105 is closed by two end caps 106 and 107 to form a muffler housing compartment 120.

FIG. 2 is a schematic perspective view of the muffler of FIG. 1 with the housing and optional fibers of the muffler removed to clearly show the internal structure of the muffler. As shown in fig. 2, the muffler has three partitions 108,109, and 110. These partitions, together with the two end caps 106, 107, divide the muffler shell compartment 120 into four chambers: between the endcap 106 and the diaphragm 108 is a first chamber 201, between the diaphragm 108 and the diaphragm 109 is a second chamber 202, between the diaphragm 109 and the diaphragm 110 is a third chamber 203, and between the diaphragm 110 and the endcap 107 is a fourth chamber 204. As shown in fig. 2, only the partition 108 of the three partitions 108,109 and 110 may or may not be provided with small holes, so that the chamber 201 may be sound-insulated from the other chambers 202,203 and 204. The partitions 109 and 110 are provided with small holes so that the chambers 202,203 and 204 are not sound-insulated. Thus, the three chambers 202,203 and 204 constitute a large volume of the acoustic cavity.

The muffler further includes a return pipe 111 (discussed in detail below) and a control device 104 disposed in the outlet pipe 102. The control device 104 may control the muffler to operate in one of two operating modes. In fig. 1 to 14, an embodiment of the control device 104 is shown as a valve which can be opened or closed to switch the mode of operation of the muffler. However, it should be understood by those skilled in the art that other forms of control means may be used in the present invention, provided that the control means is capable of controlling/being controlled to effect switching between muffler operating modes.

Fig. 3 further shows the internal structure of the muffler of fig. 1, including an inlet pipe, two outlet pipes, a return pipe, and a plurality of partitions. As shown in fig. 3, the inlet pipe 101 extends from the end cap 106 to provide a connection to the muffler to the engine in which it is installed. The input pipe 101 passes through baffles 108,109 and 110 and terminates in a chamber 204 (additional baffles 112 will be discussed in another embodiment). The outlet pipe 102 begins in the chamber 202, passes through the partitions 109 and 110, and finally extends from the end cover 107 to the exterior of the muffler shell compartment 120. The control device 104 is arranged near the end of the output tube 102. In this embodiment, the control device 104 is a valve 104. The output pipe 103 begins in chamber 201, passes through the partitions 108,109 and 110, and finally extends from the end cover 107 to the exterior of the muffler shell compartment 120. The return pipe 111 begins in chamber 202, passes through the partitions 109 and 110, and terminates in chamber 204.

In fig. 3, the portion of the inlet pipe 101 within the chamber 201 is provided with a set of small holes 303. The return pipe 111 is provided with a small hole 304 in a portion inside the chamber 203. Through the two ends of the return tube 111 and its small holes 304, the return tube 111 forms an acoustic path between the chambers 202,203 and 204, allowing acoustic flow between these chambers. Similarly, as shown in FIG. 3, output tubes 102 and 103 may be provided with their own orifices 305 and 306 in respective portions of chamber 203. The apertures in output tubes 102 and 103 are used to mount the sleeve resonators. The portions of output tubes 102 and 103 having apertures 305 and 306 are used to mount the sleeve resonator to reduce high frequency noise (described in more detail below). However, embodiments in which output tubes 102 and 103 are not apertured and no sleeve resonator is installed do not depart from the principles of the present invention. In an alternative embodiment, another spacer 112 may be provided between spacer 110 and end cap 107, with output tubes 102 and 103 passing through spacer 112. Thus, as shown in FIG. 3, the partition 110 and the inserted partition 112 form a chamber 205, and the inserted partition 112 and the end cap 107 form a chamber 206. In another alternative embodiment, at least one of the output tubes is provided with a high frequency sleeve resonator. As shown in fig. 3, a high-frequency double-pipe resonator S1+ M1 is provided on the output pipe 102, and a high-frequency double-pipe resonator S2+ M2 is provided on the output pipe 103. The diameters of the sleeves M1 and M2 are slightly smaller than the corresponding diameters of the high-frequency resonators S1 and S2, so that the sleeves M1 and M2 are mated with the resonators S1 and S2, respectively. The potential "whistle noise"/"whistle" can be addressed by making small holes in the resonators S1 and S2. In addition, by increasing the number of small holes in the resonators S1 and S2, interference with other parts of the muffler can be further achieved. Preferably, the high-frequency sleeve resonator is a stainless steel high-frequency sleeve resonator.

Two modes of operation of the muffler according to the present invention are discussed below. A muffler according to the present invention is operable to select one of two modes of operation by opening or closing the valve 104.

FIG. 4 is a schematic view of the exhaust path of a first embodiment of the muffler of the present invention operating in a first mode of operation ("pure Helmholtz" design or "pure Helmholtz mode"), including the Helmholtz cavity and Helmholtz neck. In this "pure Helmholtz mode", the valve 104 at the end of the outlet pipe 102 is in a closed state. This mode is designed to operate when the engine is running at low speed. In this mode, because the baffle 108 does not have small holes in it in this embodiment, the baffle 108 divides the muffler shell compartment 120 into two distinct sections: chamber 201 alone is the first compartment and chambers 202,203 and 204 constitute the second compartment. In the present embodiment, the first section is sound-insulated from the second section. Since the exhaust path is the only path out as indicated by the solid arrows in FIG. 4, the exhaust flows from the small holes 303 in the inlet pipe 101 to the chamber 201 and directly to the outlet pipe 103, thus changing the second region of the muffler housing compartment 120 to a Helmholtz chamber. The helmholtz neck is the portion of input pipe 101 between orifice 303 and the end of input pipe 101 in the helmholtz cavity, which is the volume of the second compartment of muffler shell space 120. In this "pure helmholtz mode", the muffler has a high sound-damping effect at the helmholtz resonance frequency, with the back pressure being kept below the first preset target value.

FIG. 5 is a graph showing the muffling efficiency of the muffler operating in "pure Helmholtz mode". The X-axis represents frequency and the Y-axis represents damping effect. The frequency of maximum muffling effect when the muffler is operating in "pure helmholtz mode" can be calculated by:

wherein:

c is speed of sound

A is the cross-sectional area of the Helmholtz neck, i.e. the cross-sectional area of the inlet pipe 101

V Helmholtz Chamber volume, volume in the second Interval of the muffler housing 120

L-length of Helmholtz neck, i.e. the length of inlet pipe 101 between the orifice and the end of inlet pipe 101 in the Helmholtz cavity

As can be seen from the above equation and fig. 5, when the engine is running at low speed, the "pure helmholtz mode" has a very high acoustic efficiency for low exhaust pulsation frequencies (pulsing frequencies), while maintaining the back pressure below the first preset target value. The first operating mode is therefore designed to keep the back pressure below the first target value at low exhaust frequencies (typically not higher than 100 Hz), which correspond to low engine speeds, typically 1000 to 2500 revolutions per minute. As an example, the first preset target value may be: 50mbars when the engine speed is 2500 rpm or 50mbars when the engine mass flow rate is 250 kg/h. It can also be defined by the equivalent section Se given by the system:

fig. 6 is a schematic perspective view showing the exhaust path when the muffler of the present invention is operating in a "pure helmholtz mode". In fig. 6, exhaust gas is drilled through a small hole 303 in the inlet pipe 101, enters one end of the outlet pipe 103 in the chamber 201, and then is discharged from the other end of the outlet pipe 103. When the engine is operated at low rotational speeds (typically 1000 to 2500 rpm), it generates low frequency noise (typically less than 100 Hz) which requires either a large tuning volume or a large back pressure for a conventional muffler. When operating in this speed range, the muffler according to the present invention is placed in a "pure helmholtz mode" by closing the valve 104, so that the muffler is now acoustically equivalent to a pure helmholtz design, which has a high acoustic efficiency at low exhaust pulsation frequencies while keeping the back pressure below a preset target value.

Fig. 7 shows an acoustic equivalent or lumped model of the muffler of the present invention operating in "pure helmholtz mode". In this mode, the sound wave from the input pipe 101 is split into two sound paths. As shown in fig. 7, the sound waves passing through path a pass out of the small holes 303 in the input pipe 101 to the chamber 201 and then into the output pipe 103. The sound waves passing through path B reach the volume formed by chambers 202,203 and 204 by input pipe 101, and since there are small holes in baffles 109,110 and in return pipe 111, there is no acoustic isolation between these chambers. Thus, the Helmholtz neck in this mode is the portion of input tube 101 after orifice 303, and the Helmholtz volume is comprised of chambers 202,203, and 204.

It should be understood that "pure Helmholtz mode" is only one embodiment of the first mode of operation. Alternatively, the first mode may be a "helmholtz with leakage mode" in which only a very small number of small holes are provided in the baffle 108. These apertures are typically less than 20 holes (e.g., 15 holes) about 3.5 millimeters (mm) in diameter, thereby allowing noise and/or gas to escape through the apertures between chamber 201 and chambers 202,203, and 204. In this Helmholtz mode with leakage, first chamber 201 is not completely acoustically isolated from the other chambers, but is in limited acoustic communication. The damping efficiency comparison between "pure helmholtz" design/"pure helmholtz mode" and "helmholtz with leakage" design/"helmholtz mode with leakage" is shown in the table of fig. 5. Similar to the "pure Helmholtz mode", in the "Helmholtz with leakage mode" all of the exhaust gas passes through small holes 303 in inlet pipe 101 to chamber 201 and is directly exhausted by outlet pipe 103. Likewise, a muffler in "helmholtz with leakage mode" has a high muffling efficiency at the helmholtz resonance frequency, while keeping the back pressure below the first preset target value.

It will be appreciated that, depending on the different silencing efficiency requirements, small holes may be provided in at least one of the return pipe 111, the partition 109 and the partition 110, without departing from the invention, so that the chambers 202,203 and 204 are in acoustic communication with each other.

Fig. 8 schematically illustrates the exhaust path of the muffler of the present invention when operating in a second mode of operation, the "interference (plus absorption) mode", in which the valve 104 is open. This mode is designed for engine operation at medium to high speeds. In this mode, outlet tube 102 is open due to the open valve, which provides two paths for exhaust. The first path is shown in FIG. 8 by the dashed arrow and is discharged in chamber 201 through outlet pipe 103 by small hole 303 in inlet pipe 101. The second of the two exhaust paths is shown by the solid arrows in fig. 8, from the inlet pipe 101 in the chamber 204 to the return pipe 111 and then in the chamber 202 into the outlet pipe 102, and finally out through the outlet pipe 102. Because the overall resistance to airflow traveling along the second exhaust path is much less than the overall resistance to airflow traveling along the first exhaust path, a large portion of the exhaust flow is exhausted along the second path. This mode is referred to as the "interference" design or "interference mode". In this mode, a majority (approximately 80%) of the exhaust flow is exhausted along the second exhaust path, with the remaining approximately 20% of the exhaust flow escaping through the first exhaust path. From the above, it can be seen that the exhaust path through which most of the exhaust gas flows in the "disturbance mode" is separate from the exhaust path through which the exhaust gas flows in the "pure helmholtz mode" or the "leaky helmholtz mode".

In embodiments where baffle 112 is positioned between baffle 110 and end cap 107, the mode of operation of the muffler may be changed to a "disturbance plus absorption mode" by virtue of fibers 301 in chamber 203 and/or fibers 302 in chamber 206. In such an embodiment, the space of the chamber 203 is partially or completely filled with fibers 301. Likewise, the space of the chamber 206 may be partially or fully filled with fibers 302.

The overall muffling efficiency in the second mode of operation is generally as shown in fig. 9. The X-axis represents frequency and the Y-axis represents damping effect. The graph in fig. 9 shows that the acoustic efficiency in the "interference (plus absorption) mode" is higher at medium and high frequencies when the engine is operating at medium and high speeds, while the back pressure can be kept below the second preset target value. Examples of the second preset target value are: the target value may be set at 150mbars when the engine speed is 6000 rpm or when the engine mass flow rate is 600 kg/h. It can also be defined by the equivalent section Se:

it will be seen by those skilled in the art that the equivalent cross-section is increased due to the valve opening. This means that the system is more easily passed. The second operating mode is therefore designed to achieve high efficiency at medium and high exhaust frequencies (typically above 100 Hz) corresponding to medium and high engine speeds (typically 2500 to 6000 rpm) while maintaining the back pressure below the second preset target value. Please note that the above first and second preset target values may be the same or different.

Fig. 10 is a schematic perspective view of the exhaust path of the muffler of the present invention operating in a second mode of operation (a jamming (plus absorbing) mode). In fig. 10, most of the exhaust gas flows from the input pipe 101 to the return pipe 111 and then is discharged from the output pipe 102 (solid path); only a small portion of the exhaust gas leaks out of the small hole 303 of the inlet pipe 101 and flows to the outlet pipe 103 (broken line path). When an engine is running at medium to high speeds (typically 2500 to 6000 rpm), it generates mid to high frequency (typically above 100 Hz) noise which requires less tuning volume and is more easily handled by the "interference (plus absorption) mode" in which the valve 104 is open in this embodiment.

Fig. 11 is a schematic diagram of an acoustic equivalent or lumped model of the muffler of the present invention operating in a second mode of operation ("interference (plus absorption) mode"). In this mode, the sound wave is divided into at least four paths after entering the muffler through the input pipe 101. As shown in fig. 11, path C in the "interference plus absorption mode" is the same as path a in the "pure helmholtz mode" and passes from aperture 303 to chamber 201 to outlet pipe 103. Path D is the main path in "interference plus absorption mode" via inlet pipe 101, chamber 204, return pipe 111, chamber 202 and then to outlet pipe 102. Path E is via inlet tube 101, chamber 204, septum 110, chamber 203, optional fibers 301, septum 109 to chamber 202. Path F is via the input tube 101, chamber 204, return tube 111, through the small hole 304 in the return tube 111 to the chamber 203 and optionally the fibre 301. The sound waves passing through path D, path E, and path F meet and merge together, creating different disturbances to the sound waves.

Fig. 12 shows the combined acoustic efficiency achieved by the muffler of the present invention when the engine is operated in the first mode of operation at low engine speeds and in the second mode of operation at medium and high engine speeds. In the figure, the X-axis represents frequency and the Y-axis represents sound attenuation effect. As shown in fig. 12, the muffler according to the present invention has high sound-deadening efficiency at low, medium, and high frequencies while maintaining a low back pressure. Therefore, the volume of the required sound cavity can be reduced through the invention, and the efficiency of the engine during acceleration or deceleration is greatly improved.

Referring to FIG. 3 above, in another embodiment, if sleeve resonator S1+ M1 is partially assembled with output tube 102 in chamber 203 and/or S2+ M2 is partially assembled with output tube 103 in chamber 203, respectively, the main air path in the second mode flows through input tube 101 and return tube 111 and through sleeve resonator S1+ M1 before being exhausted from output tube 102. Similarly, in the first and second modes, for the acoustic path into chamber 201 via apertures 303 in input pipe 101, the exhaust gas also passes through the sleeve resonator S2+ M2 before exiting from output pipe 103.

Alternatively, the valve 104 of the above-described embodiment of the present invention may be a passive self-activated valve that can be opened or closed by the pressure in the muffler. The pressure threshold for opening or closing the valve can be set according to the specific acoustic conditions required for muffler operation.

Preferably, the valve 104 may be an active valve that is electrically driven by a control signal from within or outside the muffler. The control signal may be a signal reflecting a state/states of the engine to which the muffler is connected, for example a signal reflecting at least one of the following states: the acoustic pulse frequency of the exhaust gas, the rotational speed of the internal combustion engine, the mass flow rate of the engine, and the back pressure of the exhaust system. The signal reflecting the above state may be sensed by a sensor (which may be installed inside or outside the muffler, not shown in the drawings) on the vehicle and then transmitted to the valve by a control line (which may be installed inside or outside the muffler, not shown in the drawings) to select an operation mode. For purposes of illustration and not limitation, the threshold value of the control signal may be set to 2000 revolutions per minute when the engine is running from 1000 to 6000 revolutions per minute (acceleration); the threshold value for the control signal may be set to 3000 revolutions per minute when the engine is running from 6000 to 1000 revolutions per minute (deceleration). Depending on the type of valve 104 used, the valve 104 may be disposed at various locations along the outlet pipe 102, such as at either end of the outlet pipe 102 or in the middle thereof. It is contemplated that the valve 104 may be disposed on the outlet pipe 102 in any position that controls the opening and closing of the outlet pipe 102. Alternatively, the valve 104 may be a pneumatic or hydraulic valve. Similarly, the pneumatic or hydraulic valves are controlled with the same control signals to enable the muffler to operate in the first mode path at low speeds and in the second mode path at medium and high speeds.

The above description of the change of the operation mode by the opening and closing of the valve 104 is only one embodiment of the present invention, in which the relationship between the opening and closing states of the valve and the control signal follows a binary function relationship. As shown in fig. 13, in this embodiment, the control signal follows a binary function of 0-1, with the valve 104 having substantially no intermediate states from closed to fully open (e.g., when the engine speed rises to about 1750 revolutions per minute) or from fully open to closed (e.g., when the engine speed falls to about 3250 revolutions per minute). In another more preferred embodiment of the invention, the valve 104 opens or closes according to a linear function of engine speed, which follows a linear functional relationship. In this linear embodiment, the valve 104 is fully closed when the engine is running up, when the engine is below 2000 revolutions per minute. As shown in fig. 14, the valve 104 opens linearly following a linear function at engine speeds between 2000 and 3000 revolutions per minute. For example: 25% open at 2250 rpm, 50% open at 2500 rpm, 75% open at 2750 rpm, and all open at 3000 rpm. When the engine is above 3000 rpm, the valve remains fully open. Likewise, when the engine is decelerating, the valve 104 is closed linearly, for example, between 3000 and 2000 revolutions per minute. Note that the linear open/close speed range of the valve described above of 2000 to 3000 revolutions per minute is for exemplary purposes only. It should be appreciated that the valve may be operated linearly over different speed ranges.

The two modes "pure helmholtz mode" and "interference (plus absorption) mode" selected by the valve 104 described herein are for illustrative purposes only and should not be considered as limiting the invention. Any application of the two modes to a muffler using the concept of the present invention should be considered as an application of the present invention.

Those skilled in the art will readily recognize that while a certain number of outlet pipes and exhaust paths are disclosed in the above embodiments, the number of outlet pipes and exhaust paths of the muffler of the present invention should not be limited to the specific number disclosed in the above embodiments. One skilled in the art can select any number of output tubes and exhaust paths for the muffler as desired, such as 3 or more, and this should not be considered as beyond the scope of the present invention.

Although only the preferred embodiments of the present invention have been disclosed herein, those skilled in the art will appreciate that many modifications are possible in the practice of the invention.

Claims

1. A dual mode muffler for an exhaust system of an internal combustion engine, the muffler comprising:

a housing (105);

a first end cover (106) and a second end cover (107) respectively located at both ends of the housing (105) to form a muffler housing compartment (120) together with the housing (105);

an input pipe (101) extending outwardly from the first end cover (106) to receive exhaust gas from the internal combustion engine;

a plurality of outlet pipes (103,102) extending outwardly from the second end cover (107) and forming a plurality of exhaust paths with the inlet pipe (101) and the muffler shell compartment (120); and

a control device (104) provided on one of the output pipes for operatively switching the muffler to a first or second operating mode depending on one or more conditions of the internal combustion engine, each operating mode defining a corresponding exhaust gas path through which at least a majority of the exhaust gas is conveyed, the exhaust gas path corresponding to the first operating mode being different from the exhaust gas path corresponding to the second operating mode.

2. A dual mode muffler according to claim 1, wherein the first operating mode is designed to reduce noise while maintaining the back pressure below a first preset target value when the internal combustion engine is operating at low speed, and the second operating mode is designed to reduce noise while maintaining the back pressure below a second preset target value when the internal combustion engine is operating at medium or high speed, wherein the first preset target value and the second preset target value may be the same or different, preferably the first and second preset target values are defined as preset back pressures for a given mass flow rate or as parameters independent of exhaust flow.

3. A dual mode muffler according to claim 2, wherein the exhaust path corresponding to the first mode of operation is substantially separated from the exhaust path corresponding to the second mode of operation within the muffler shell space (120).

4. A dual mode muffler according to any one of claims 1, 2 and 3, wherein the control means comprises a valve that can be opened or closed for switching the operation mode of the muffler.

5. The dual mode muffler according to claim 4, wherein said valve is a passive valve, the opening or closing of which is controlled by the pressure inside said muffler.

6. The dual mode muffler according to claim 4, wherein the valve is an active valve controlled by a control signal, preferably the active valve is selected from the group consisting of an electric valve, a pneumatic valve, and a hydraulic valve.

7. The dual mode muffler according to claim 6, wherein said control signal reflects at least one of the following conditions: the pulsation frequency of the acoustic waves of the exhaust gas, the rotational speed of the internal combustion engine, the mass flow rate of the internal combustion engine, and the back pressure of the exhaust system.

8. A dual mode muffler according to claim 6 or 7, wherein the relationship between the open and closed states of the valve and the control signal follow a given function, preferably a binary function or a linear function.

9. The dual mode muffler according to claim 4 wherein said first mode of operation is a "pure Helmholtz" design or a "Helmholtz with leakage" design and/or said second mode of operation is a "disturbance" design or a "disturbance plus absorption" design.

10. The dual mode muffler according to claim 9, further comprising:

a first partition (108), a second partition (109) and a third partition (110) placed in sequence within the housing (105), wherein,

the first (108), second (109) and third (110) partitions the muffler shell compartment (120) into four chambers: a first chamber (201) between the first end cap (106) and the first separator (108), a second chamber (202) between the first separator (108) and the second separator (109), a third chamber (203) between the second separator (109) and the third separator (110), and a fourth chamber (204) between the third separator (110) and the second end cap (107),

wherein,

the second chamber (202), the third chamber (203) and the fourth chamber (204) are in acoustic communication with each other.

11. A dual mode muffler according to claim 10 wherein the inlet pipe (101) passes through the first (108), second (109) and third (110) baffle plates and terminates in a fourth chamber (204), wherein the inlet pipe (101) is provided with a set of small holes (303) in the portion of the inlet pipe within the first chamber (201);

a first outlet pipe (103) of the plurality of outlet pipes originating from the first chamber (201), passing through the first, second and third partitions (108,109,110) and extending outside the muffler shell compartment (120) through the second end cap (107);

a second outlet pipe (102) of the plurality of outlet pipes originates in the second chamber (202), passes through the second partition (109) and the third partition (110), and extends outside the muffler shell compartment (120) through the second end cover (107); and,

the dual mode muffler also includes a return pipe (111), the return pipe (111) beginning in the second chamber (202), passing through the second and third partitions (109, 110), and terminating in a fourth chamber (204).

12. The dual mode muffler according to claim 11, wherein the plurality of orifices are provided in at least one of the following: the second separator (109), the third separator (110) and the return pipe (111), preferably provided with a small hole (304) in the part of the return pipe inside the third chamber (203).

13. A dual mode muffler according to any one of claims 10-12, characterized in that there are no small holes in the first baffle (108), thereby allowing the first chamber (201) to be acoustically isolated from the other chambers in the first mode of operation of the "pure helmholtz" design.

14. A dual mode muffler according to any of claims 10-12, characterized in that a very small number of small holes are provided in the first baffle (108), thereby providing limited acoustic communication of the first chamber (201) with each other chamber in the first mode of operation of the "helmholtz with leakage" design.

15. A dual mode muffler according to any one of claims 10-12 further comprising a fourth baffle (112) located between said third baffle (110) and said second end cap (107) to allow said first and second outlet pipes (103,102) to pass through said fourth baffle (112); a fifth chamber (205) formed between the third partition plate (110) and the fourth partition plate (112); and a sixth chamber (206) formed between the fourth separator (112) and the second end cap (107), preferably the dual mode muffler further comprises fibers (301, 302) disposed within the third chamber (203) and/or the sixth chamber (206).

16. A dual mode muffler according to any one of claims 10-12, characterized in that the first outlet pipe (103) is provided with a small hole (306) in the part of the third chamber (203) and the second outlet pipe (102) is provided with a small hole (305) in the part of the third chamber (203).

17. The dual mode muffler according to claim 16 further comprising one or more sleeve resonators (S1 + M1, S2+ M2) disposed on a portion of the first output pipe (103) and/or the second output pipe (102) located within the third chamber (203).

18. A dual mode muffler according to claim 17, characterized in that the sleeve resonator is a high frequency sleeve resonator, preferably a high frequency stainless steel sleeve resonator.