VARIABLE SOUND EXHAUST SYSTEM FOR A VEHICLE

TECHNICAL FIELD

The present subject matter described herein, in general, relates to exhaust systems for vehicles and in particular, relates to a variable sound exhaust system for two-wheelers.

BACKGROUND

Generally, an exhaust system in a vehicle releases exhaust gases, produced due to the combustion of an air-fuel mixture inside the engine of the vehicle, into the atmosphere. In addition, the exhaust system significantly reduces noise, which is usually produced by the exhaust gases coming out of the exhaust system at a high speed.

With the advent of technology, vehicles have now evolved into different categories, such as, passenger vehicles and racing vehicles, each having a different exhaust system for providing different exhaust sound effects. For the passenger vehicles, in which comfort level should be eminent, the exhaust system is designed such that either the exhaust sound is reduced to a near inaudible level or a pleasant sound effect is heard. Conversely, for racing vehicles, which are driven for fun and excitement at high speeds, the exhaust system is designed to complement the power output and thrust of the engine by minimizing power loss within the exhaust system. Due to this feature, such vehicles produce an enhanced sound effect having enhanced characteristics in terms of intensity, frequency, amplitude, velocity, etc.

The enhanced exhaust sound effect is desirous for fun, excitement, sports, and adventure purposes, and therefore the reason behind having a noisy vehicle such as a racing bike. However, such a vehicle is not preferred while on a family outing or during a visit to a public place because of the sound it creates. Thus, the racing vehicle is unsuitable for various other purposes such as the aforementioned specific outing purposes.

To overcome these limitations, people modify their vehicles to a specific sound characteristic, either low or high. However, such a modification is irreversible and would also affect the performance and safety standards of the vehicle. Additionally, success of such modifications is largely dependent on the expertise of the mechanic or workmen

hired to do the said job. In some cases, after the modification process, two separate silencers need to be installed to achieve ambient sound levels desired by the rider,

In order to get low exhaust sound effect, vehicles employ methods such as increasing the surface area of the portion where exhaust gases expands, called as muffler, or using two tail pipes. All these methods increase the overall size of the exhaust system including the muffler and also add up to the manufacturing cost of the vehicle. One more technical solution, which guarantees nearly inaudible sound, is to use a controlled system that includes an actuating element such as movable pipes having holes to control the flow of the exhaust gases on them. Further, the controlled system is provided with one or more movable expansion chambers, and a gear mechanism for motion transmission of the actuating element. However, such a solution is extremely complex and leads to unstable flow conditions of the exhaust gases. Moreover, such solution has a large number of moving parts like expansion chambers, pipes and gears which are prone to wear and tear. Also, in the event of improper gear meshing, undesirable sound effects are produced leading to disturbance to both the rider and his surrounding.

Therefore, there is a need for an exhaust system that can provide both high and low exhaust sound effect at all operating conditions of the engine. The exhaust system should be easy to install without any modification in existing frame structure of the vehicle, cost- effective and user friendly. Finally, it is desired that the aesthetics of the vehicle along with the exhaust system remains in tact.

SUMMARY

The subject matter described herein is directed to an exhaust system for a vehicle, preferably a two-wheeler, such as a motorcycle. However, the exhaust system can be implemented in other vehicles also and should not be considered limited to two wheelers only.

The exhaust system includes an exhaust pipe and a muffler for transferring exhaust gases from an internal combustion (IC) engine of the vehicle into the atmosphere. An end of the exhaust pipe is connected to an exhaust port of the IC engine as an intake for the exhaust gases from the IC engine while another end is connected to the muffler. The

exhaust gases leave the exhaust system from an outlet port provided at an extreme end of the muffler.

The exhaust system is capable of providing variable exhaust sound effects. For the purpose, the system includes at least a first passage and a second passage defined by a plurality of expansion chambers and a plurality of pass-through in the muffler. The first passage releases the exhaust gases to generate a first predetermined exhaust sound effect whereas the second passage releases the exhaust gases to generate a second predetermined exhaust sound effect. The second predetermined exhaust sound effect is higher than the first predetermined exhaust sound effect owing to the enhanced sound characteristics in terms of intensity, frequency, amplitude, velocity, etc., of the second predetermined exhaust sound effect. The exhaust system further includes a switching mechanism for selectively opening either the first passage or the second passage for releasing the exhaust gases into the atmosphere and to get the desired sound effect.

These and other features, aspects, and advantages of the present subject matter will be better understood with reference to the following description and appended claims. This Summary is provided to introduce a selection of concepts in a simplified form. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor it is intended to be used to limit the scope of the claimed subject matter.

BRIEF DESCRIPTION OF DRAWINGS

The above and other features, aspects, and advantages of the subject matter will become better understood with regard to the following description, appended claims, and accompanying drawings where:

Figure 1 shows an exemplary exhaust system, for a two-wheeler, for providing variable exhaust sound modes, in accordance with an embodiment of the present subject matter.

Figure 2A shows a muffler of the exhaust system of Figure 1 providing a first and a second passage and a plunger mechanism for providing variable exhaust sound modes, in accordance with an embodiment of the present subject matter.

Figure 2B shows a magnified view of the plunger mechanism illustrated in Figure 2A.

Figure 2C schematically illustrates the plunger mechanism as illustrated in Figure

2A.

Figure 3A shows a muffler employing a single valve mechanism, in accordance with an embodiment of the present subject matter.

Figure 3B shows a magnified view of the single valve mechanism illustrated in Figure 3A.

Figure 4A shows a muffler employing a double valve mechanism, in accordance with an embodiment of the present subject matter.

Figure 4B shows a magnified view of the double valve mechanism illustrated in Figure 4A.

DETAILED DESCRIPTION

The subject matter described herein relates to an exhaust system for a vehicle that provides variable exhaust sound modes wherein each mode has a predetermined sound effect. The sound effect generated due to exhaust gases is determined by characteristics such as sound level, pitch, frequency, of the sound. Sound is mainly produced due to the release of exhaust gases from an internal combustion (IC) engine, at a high speed, through a narrow pipe, also called as exhaust pipe, provided in the exhaust system. The exhaust system includes an exhaust pipe, which has an inlet port, and a muffler having an outlet port to release exhaust gases into the atmosphere. One end of the exhaust pipe, i.e., the inlet port, is connected to an exhaust port of the engine to intake the exhaust gases from the engine while the other end is connected to the muffler. The exhaust gases finally leave the exhaust system from the outlet port of the exhaust pipe via the outlet port provided at outer extreme end the muffler.

The muffler further includes a plurality of passages with at least a first passage and a second passage, for the flow of the exhaust gases, to provide variable exhaust sound modes. In a first mode of exhaust sound, the first passage is utilized. The first passage releases the exhaust gases from the outlet port of the exhaust pipe to generate a first

predetermined sound effect, which is nearly inaudible or has a pleasant sound effect. Similarly, in a second mode of exhaust sound the second passage is utilized. The second passage releases the exhaust gas from the outlet port to generate a second predetermined exhaust sound effect suitable for high speed ride, and racing purposes. In order to switch between the two modes of exhaust sound, the exhaust system includes a switching mechanism for selectively choosing a passage for flow of the exhaust gases. The switching mechanism can be actuated manually or electrically for selecting the desired passage for flow of the exhaust gas.

The exhaust system may be implemented in any two-wheeled vehicle such as a motorcycle, scooter, step-through vehicle, all terrain bike, etc.. Further, the exhaust system may be implemented to provide variable exhaust sound mode wherein two or more different exhaust sound modes may be achieved. However, for the purpose of explanation and by no limitation, the exhaust system described here achieves two exhaust sound mode.

Figure 1 illustrates an exhaust system 100 for a vehicle providing two different sound modes using two different passages for exhaust gases.

The exhaust system 100 as described herein is for the purpose of releasing hot and noxious gases, also known as exhaust gases, produced during the combustion of air-fuel mixture in the IC engine (not shown in the figure) of the vehicle. The exhaust system 100 also performs the function of reducing exhaust emissions and dampening the sound generated during the release of the exhaust gases during an exhaust cycle of the IC engine. In one embodiment of the present subject matter, the exhaust system 100 is mounted on a frame structure of the vehicle by means of brackets (not shown in the figure) such as clamps and rubber mounts.

The exhaust system 100 includes an exhaust pipe 102 provided with an inlet port 104 and a muffler 106 provided with an outlet port 108. The inlet port 104 is connected to an exhaust port of the IC engine (not shown in the figure). The exhaust gases, through the exhaust port of the IC engine and the inlet port 104, enter the exhaust pipe 102. In different implementations, the exhaust pipe 102 can be a single long tube or an assembly of tubes connected to form a single tubing. The exhaust pipe 102 cleans the exhaust gases such that no harmful emission are released into the atmosphere. In one implementation, a plurality of catalytic converters can be placed along the length of the exhaust pipe 102 for

reducing exhaust emissions. The exhaust gases then passes through the muffler 106 and are released into atmosphere through the outlet port 108 present at the outer extreme end of the muffler 106.

The muffler 106 varies the sound characteristic such as sound level, pitch etc., of the exhaust gases before the exhaust gases are released into the atmosphere by using reflection technique already known in the art. In one embodiment of the present subject matter, the muffler 106 houses a plurality of expansion chambers 110 separated by a plurality of pass-through collectively referred to as pass-through 112. In one embodiment, the pass-through 112 may include pipes of equal or varying diameter.

For the purpose of explanation and by no means to limit the scope of the subject matter, the muffler 106 of the exhaust system 100 includes three chambers 110, namely, a first expansion chamber 110-1, a second expansion chamber 110-2, and a third expansion chamber 110-3. The cross-sectional area of the expansion chambers 110 and the distance between two successive expansion chambers 110 determine the exhaust sound effect of the exhaust gases and can be varied in the muffler 106. In one embodiment, the expansion chambers 110 have equal cross-sectional area.

The first expansion chamber 110-1 is placed such that the exhaust gases from the exhaust pipe 102 enters the first expansion chamber 110-1 of the muffler 106. The exhaust pipe 102 is partially inserted into the muffler 106 from one end and is connected to the first expansion chamber 110-1 through a pathway 114. The third expansion chamber 110-3 is disposed at the proximity of the outlet port 108 of the muffler 106. The second expansion chamber 110-2 is located in between the first expansion chamber 110-1 and the third expansion chamber 110-3. The flow of the exhaust gases from one of the expansion chambers 110 to the other is directed through various passages, such as the first and second passage, defined by a plurality of pass-through 112 provided between the expansion chambers 110. In one embodiment, these pass-through 112 are in the form of holes of same diameter. In another embodiment, small metallic pipes, all having a substantially small diameter can be used. Thus, the pass-through 112 can be construed as tubular pipes connecting the expansion chambers 110. It will be understood that, there can be various possible variants and combinations available to the aforesaid feature.

Figure 2A shows the muffler 106 of the exhaust system 100 providing the first and second passage and a switching mechanism for providing variable exhaust sound modes. In accordance with a first embodiment of the present subject matter, the switching mechanism is implemented employing a plunger mechanism 200. As shown, in this. embodiment, the plurality of pass-through 112 include a first pass-through 112-1, and a second pass-through 112-2.

The first passage is used when the vehicle is operated in the first mode of exhaust sound. In the first mode of exhaust sound, the exhaust gases flow from the first expansion chamber 110-1 to the third expansion chamber 110-3 through the first pass-through 112-1 and subsequently to the second expansion chamber 110-2 through an intermediate pass- through (not shown in figure). Finally the exhaust gases exit the exhaust system 100 from the second expansion chamber 110-2 into the atmosphere through another pass-through 112-2 connected to the outlet port 108 (shown in fig.l). This flow of the exhaust gases defines the first passage providing the flow of the gases along the various chambers 110.

The second passage is defined by the pass-through 112 connecting the first expansion chamber 110-1 and the outlet port 108. When flowing through the second passage, the exhaust gases flow from the first expansion chamber 110-1 to the third expansion chamber 110-3 through the first pass-through 112-1 and subsequently to the outlet port 108 through the .pass through 112-2.

As explained before, the first passage provides the first mode of exhaust sound. In the first mode, the exhaust gases are released to generate a first predetermined sound effect. The first predetermined sound effect ensures negligible sound pollution, less distraction and high comfort level to a rider of the vehicle. Thus, the first mode is also referred to as the cruise mode. Similarly, the second passage provides the second mode of exhaust sound, wherein, the second predetermined sound effect is generated. The second predetermined sound effect provides enhanced sound effects and can have effects such as racing bike sound effect. Thus, the second mode is also referred to as the racing mode.

In order to enable a user to switch between the two exhaust sound modes, the switching mechanism is included for selectively choosing between the first passage and the second passage. The switching mechanism provides either a fully open position or a fully closed position for one of the two passages at one time and may include mechanisms

such as a valve mechanism or a plunger mechanism. The switching mechanism can be actuated by using several methods. In one implementation, the switching mechanism can be actuated mechanically by pressing a pedal connected to the switching mechanism. In another implementation, the switching mechanism can be actuated by an electronic controller using sensors and electromechanical devices. The switching mechanism can switch between two or more exhaust sound modes at a predefined speed and load condition while the IC engine is in operation.

In accordance with the present embodiment of the present subject matter, the switching mechanism is implemented employing a plunger mechanism 200. The plunger mechanism 200 works as the switching mechanism for selectively opening either the first passage or the second passage for the flow of the exhaust gases out of the exhaust system 100. The plunger mechanism 200 is placed at the second pass-through 112-2 and operates in two positions, i.e., a fully open position and a fully closed position. The plunger mechanism 200 employs a spring loaded plunger (described later) actuated by an actuating wire 202. At an initial position, the plunger is in the fully closed position closing the passage for the flow of the exhaust gases from the third expansion chamber 110-3 to the outlet port 108 through the second pass-through 112-2.

When the first mode of exhaust sound or the cruise mode is required, the plunger mechanism 200 is not actuated and remains at the initial position, i.e., fully closed position. The exhaust gases from the inlet port 104 reach the first expansion chamber 110- 1 through the exhaust pipe 102 and flow through the first pass-through 112-1 to reach the third expansion chamber 110-3. The exhaust gases experience a change of surface area while flowing through the first pass-through 112-1 and upon reaching the third expansion chamber 110-3. The change in the surface area generates sound waves of an opposite phase upon hitting the walls of the expansion chambers 110-1 and 110-3. These reflected sound waves cancel out some portion of the initial exhaust sound waves originating from the operation of the IC engine.

As the plunger is in the fully closed position at the third expansion chamber 110-3, the exhaust gases are directed from the third expansion chamber 110-3 to the second expansion chamber 110-2 through the intermediate pass-through. Again, the flow of the exhaust gases is altered by the change in the surface area and sound waves of an opposite

phase are again generated. These opposite phase reflected sound waves further cancel out the exhaust sound waves to provide the first predetermined exhaust sound effect. The exhaust gases then flow from the second expansion chamber 110-2 through the second pass-through 112-2 and finally to the outlet port 108, thereby releasing the exhaust gases into the atmosphere with the first predetermined exhaust sound effect.

When the second mode of exhaust sound is required, the plunger mechanism 200 is actuated for bringing the plunger to the fully open position such that the second passage is opened for the flow of the exhaust gases. The plunger is opened by pulling the actuating wire 202, either mechanically or by electrical means, thereby opening a plunger- mechanized drilled passage 204 directly from the third expansion chamber 110-3 to the second pass-through 112-2. The exhaust gases are finally released into the atmosphere through the outlet port 108 connected to the second pass-through 112-2.

In the second mode, since the exhaust gases do not flow through all the expansion

^' chambers 110, the exhaust sound waves are not cancelled out and are released from the second pass-through 112-2 with the second predetermined exhaust sound effect. The opening of the plunger prevents the exhaust gases from flowing to the second expansion chamber 110-2 by closing the intermediate pass-through. Thus, the first passage is completely closed during the time the second passage is opened.

Figure 2B shows a magnified view of the plunger mechanism 200 as illustrated in Figure 2A.

As discussed in Figure 2A, the plunger mechanism 200 is fitted at the second pass- through 112-2 for opening the second passage and closing the first passage for the flow of the exhaust gases. This plunger mechanism 200, also referred to as spring loaded plunger 200, comprises a spring 206 and the plunger 208 encapsulated in a body 210 such that a tip or ball of the plunger 208 is protruding outwards from one end of the body 210. At the initial position of the spring loaded plunger 200, the plunger 208 closes a first end 212 of the plunger drilled passage 204, thus restricting the flow of the exhaust gases to the second pass-through 112-2.

Figure 2C schematically illustrates the plunger mechanism 200 as illustrated in Figure 2A and 2B.

As discussed in Figure 2A and 2B, the spring loaded plunger 200 further comprises a pin 214 mechanically coupled to the plunger 208 in the body 210. The spring loaded plunger 200 is operated by pulling the pin 214 through the actuating wire 202.

When the pin 214 is pulled out, the plunger 208 is also pulled in the direction of the pin 214, thus compressing the spring 206 inside the body 210. Due to the compression of the spring 206, a spring tension is generated in the spring 206. Under the spring tension, the plunger 208 moves the body 210 in the direction of the pull, thereby pushing the body 210 into a hole of the intermediate pass-through. Thus, the intermediate pass-through is closed and simultaneously the plunger mechanism drilled passage 204, i.e., the second passage in this embodiment, is opened for the exit of the exhaust gases.

Figure 3A shows the muffler 106 employing a single valve mechanism 300 in the exhaust system 100 in accordance with a second embodiment of the present subject matter.

In said embodiment, the expansion chambers 110 of the muffler 106, namely, the first expansion chamber 110-1, the second expansion chamber 110-2 and the third expansion chamber 110-3, are placed at an equal distance from each other. In another embodiment, the expansion chambers 110 are not equidistant and the spacing between the expansion chambers 110 is varied. The first expansion chamber 110-1 is directly connected to the outlet port 108 through a pass-through 112-3. Further, the first expansion chamber 110-1 is also connected to the third expansion chamber 110-3 through a pass- through 112-4. The third expansion chamber 110-3 is connected to the second chamber through a pass-through 112-5. The second expansion chamber 110-2 includes a pass- through 112-6, which is connected to the pass-through 112-3.

As said earlier, the muffler 106 provides two passages, the first passage and the second passage, for the flow of the exhaust gases from the IC engine to the atmosphere. The exhaust gases follow either the first passage or the second passage that start from the inlet port 104 and through the muffler 106 reach the outlet port 108. The passage to be followed by the exhaust gases in the muffler 106 is determined by the plurality of pass- through 112 connecting the expansion chambers 110-1, 110-2, 110-3, and the switching mechanism.

The present embodiment includes a single valve mechanism 300 or valve mechanism 300 as the switching mechanism for selecting the passage for the flow of exhaust gases out of the muffler 106. A single valve (not shown in the figure) is fitted in to the pass-through 112-3 and can be actuated either manually or electronically. The valve mechanism 300 provides either a fully close position or a fully open position at the pass- through 112-3 for the flow of the exhaust gases. The first passage is selected when the valve mechanism 300 closes the pass-through 112-3 and the second passage is selected when the valve mechanism 300 opens the pass-through 112-3. At an initial position, valve mechanism 300 closes the pass-through 112-3.

When the first mode of exhaust sound or the cruise mode sound is required, the mechanism 300 is at its initial position, i.e., the pass-through 112-3 is closed, thereby providing the first passage for the flow of the exhaust gases. The exhaust gases from the IC engine reach the first expansion chamber 110-1 in the muffler 106 through the exhaust pipe 102 connected to the exhaust port of the IC engine. The exhaust gases then flow from the first expansion chamber 110-1 through the pass-through 112-4 to the third expansion chamber 110-3. From the third expansion chamber 110-3, the exhaust gases move to the second expansion chamber 110-2 through the pass-through 112-5. The exhaust gases are then, from the pass-through 112-6, vented out of the second chamber 110-2 into the atmosphere via the outlet port 108.

The exhaust gases encounter a change in the surface area while flowing through the plurality of pass-through 112 and upon entering the expansion chambers 110. The change in the surface area provides a resistance to the flow of the exhaust gases, and the exhaust gases reflect a portion of their strength in the form of sound waves in a direction opposite to their travel direction, i.e., sound waves of an opposite phase are created. The reflected opposite-phase sound waves cancel out the initial sound waves of the exhaust gases, thereby reducing the exhaust sound to the first predetermined exhaust sound effect.

When the valve mechanism 300 is actuated to select the second mode of exhaust sound, i.e., the racing mode, the mechanism 300 fully opens the pass-through 112-3, thereby providing the second passage for the flow of the exhaust gases. In this case, the exhaust gases enter the inlet port 104 and reach the first expansion chamber 110-1 through the exhaust pipe 102. The exhaust gases then move from the first expansion chamber 110-

1 through the pass-through 112-3, which is opened by the mechanism 300, and are directly released into the atmosphere from the outlet port 108. The exhaust gases do not flow through all the expansion chamber and hence do not encounter much difference in the surface area. Accordingly, the exhaust gases are released into the atmosphere at a very high sound level, i.e., with the second predetermined effect, which is very near to the initial sound level of the exhaust gases coming out of the IC engine.

Figure 3B shows a magnified view of the single valve mechanism 300 as illustrated in Figure 3A.

As described in Figure 3A, the valve mechanism 300 fitted at the pass-through 112-3 employs a butterfly valve 302 for selectively switching between the first passage and the second passage. The butterfly valve 302 is in the form of a typical flow control device for providing a fully open position and a fully closed position of the valve. The butterfly valve 302 as used herein comprises a valve seat engaged by a butterfly disc. The butterfly valve 302 is mounted on a shaft (not shown in the figure) in order to rotate between the fully open position and the fully closed position. The butterfly valve is supported on the shaft by a pair of valve body housings, namely a first housing 304 and a second housing 306, on either side of the butterfly valve 302. At an initial position, when the butterfly valve 302 is at an angle of 90° with respect to the shaft, the butterfly valve

302 is said to be in the fully closed position. The butterfly valve 302 is said to be in the fully open position when the butterfly valve 302 is at an angle 0° with respect to the shaft.

The valve mechanism 300 further comprises a torsion spring 308 closely wound on the shaft. One end of the torsion spring 308 is connected to the second housing 306 while the other end is connected to a lever 310, which is mounted on an extreme end of the shaft.

The torsion spring 308 is designed to keep the butterfly valve 302 in the fully closed position, i.e., at the initial position, thus keeping the pass-through 112-3 closed and the first passage opened for the exhaust gases to flow through the pass-through 112-4. The rotation of the lever 310 by an external means rotates the torsion spring 308. The torsion spring 308 then exerts a rotational force on the second housing 306, thereby rotating the butterfly valve 302 until it is at an angle of 90° with respect to the shaft. This brings the butterfly valve 302 to the fully open position, thus opening the second passage. The torsion spring 308, under the spring tension caused due to the rotation of the lever 310,

tries to bring back the butterfly valve 302 to its original position, i.e. fully closed position. Hence, the lever 310 is rotated as long as the second mode or high exhaust sound effect is required.

Figure 4A shows the muffler 106 employing a double valve mechanism 400 in the exhaust system 100 in accordance with a third embodiment of the present subject matter.

In said embodiment, within the muffler 106, the pass-through 112-3 directly connects the outlet port 108 and the first expansion chamber 110-1, to form the second passage. In order to provide the first passage, the first expansion chamber 110-1 is connected to the third expansion chamber 110-3 through the pass-through 112-4, which is in turn connected to the second expansion chamber 110-2 through the pass-through 112-5. The second expansion chamber 110-2 is finally connected to the outlet port 108 through a pass-through 112-7. In this way, the aforesaid arrangement provides two passages for releasing the exhaust gases from the IC engine into the atmosphere, i.e., the first passage and the second passage.

A double valve mechanism 400 or mechanism 400 is used as the switching mechanism for selecting a passage for the flow of the exhaust gases. Two valves of the mechanism 400 are fitted at the pass-through 112-3 and the pass-through 112-4, respectively. The two valves, valve A and valve B (not shown in the figure but will be explained later), work simultaneously but in an alternate manner for closing and opening the pass-through 112-3 and the pass-through 112-4, respectively.

For example, the two valves can simultaneously remain in two alternate operating positions, one in fully close position and the other in fully open position. The double-valve mechanism 400 provides an opening to the first passage by fully closing the first pass- through 112-3, but fully opening the pass-through 112-4 at one instant. Likewise, the double valve mechanism 400 provides an opening to the second passage by fully closing the pass-through 112-4 but fully opening the pass-through 112-3 at another instant. At an initial position of the double valve mechanism 400, the first valve is at the fully close position and the second valve is at the fully open position. The double valve mechanism 400 can also be actuated similar to switching mechanisms described in earlier figures, i.e., electrically or manually.

When the first mode of exhaust sound is required, i.e., the cruise mode, the double valve mechanism 400 remains at the initial position. At this position, the pass-through 112-3 remains closed while the second pass-through 112-4 is opened, thereby providing the first passage for the flow of the exhaust gases. The exhaust gases from the IC engine flow through the exhaust pipe 102 connected to the exhaust port of the IC engine and reach the first expansion chamber 110-1. The exhaust gases now flow from the first expansion chamber 110-1 through the pass-through 112-4 to the third expansion chamber 110-3 and then, through the pass-through 112-5, to the second chamber 110-2. From there, the exhaust gases reach the outlet port 108 via the pass-through 112-7 and finally escape into the atmosphere generating a very low sound effect. The cause of the reduction in the level of exhaust sound is similar to what has been explained in other similar embodiments of the present subject matter.

Upon actuating the double valve mechanism 400 for selecting the second mode of exhaust sound, i.e., the racing mode sound, the double valve mechanism 400 fully opens the pass-through 112-3 and fully closes the pass-through 112-4. This arrangement opens the second passage for releasing the exhaust gases into the atmosphere. The exhaust gases from the IC engine reaches the first expansion chamber 110-1 through the exhaust pipe 102. Via the first pass-through 110-1, the exhaust gases flow from the first expansion chamber 110-1 directly to the outlet port 108. As the exhaust gases have not flown through all the expansion chambers, no opposite-phase reflected sound waves are generated to cancel out the initial sound waves of the exhaust gases coming out of the IC engine. Thus, the exhaust gases are released into the atmosphere at a high sound level or with the second predetermined sound effect.

Figure 4B shows a magnified view of the double valve mechanism 400 as illustrated in Figure 4A.

In the present embodiment, a butterfly valve of the double valve mechanism 400 having two circular disc or valve is fitted at the pass-through 112-3 and the pass-through 112-4. The first valve 402 and the second valve 404 are employed for selecting the first passage and the second passage, respectively. The first valve 402 and the second valve 404 are mounted on a shaft 406 for rotating the valves (402, 404) between a fully open position and a fully closed position. The first valve 402 and the second valve 404 are said

to be in the fully closed position at an angle of 90° with respect to the shaft 406. The first valve 402 and the second valve 404 are said to be in the fully open position at an angle of 0° with respect to the shaft 406.

The first valve 402 and the second valve 404 are placed at an angle of 90° such that, on rotation of the shaft 406, only one of the two valves (402, 404) is in fully open position. At an initial position, the first valve 402 is placed at an angle of 90° with respect to the shaft 406 and the second valve 404 is placed at an angle of 0° with respect to the shaft 406.

In addition, the first valve 402 and the second valve 404 are supported on the shaft 406 by a pair of valve body housings, namely a first housing 408 and a second housing 410, such that the first valve 402 and the second valve 404 are placed in between the pair of housings (408, 410). The double valve mechanism 400 further comprises a torsion spring 412 closely wound on the shaft 406. On one end, the torsion spring 412 is connected to the second housing 410 and to a lever 414, which is mounted on an extreme end of the shaft 406, on other end. The torsion spring 412 is mounted on the shaft 406 such that the first valve 402 is at the fully closed position and the second valve 404 is at the fully open position, i.e., the initial position. In this way, the opening of the pass- through 112-4 enables the opening of the first passage for the exhaust gases to flow out of the exhaust system 100.

In order to actuate the opening of either of the passages, the lever 412 is rotated by an external means, thus rotating the torsion spring 412 attached thereto. The torsion spring 412 exerts a rotational force on the shaft 406, thereby rotating the first valve 402 and the second valve 404. The first valve 402 is rotated until the first valve 402 is at an angle of 0° with respect to the shaft 406, thereby bringing the first valve 402 to the fully open position. Simultaneously, the second valve 404 is rotated until the second valve 404 is at an angle of 90° with respect to the shaft 406, thereby bringing the second valve 404 to the fully closed position. In this way, the second passage gets opened for the exit of the exhaust gases out of the exhaust system 106.

The spring tension in the torsion spring 412 caused due to the rotation of the lever 416 pushes the shaft 406 back to the initial position. Hence, the lever 416 is rotated as long as the second passage is used or actuated by the external means. The external means for

rotating the lever in accordance with the second embodiment and the third embodiment can be any actuating means known in the art. The lever 416 can be rotated manually by constantly pressing a pedal mechanically coupled to the lever 416 or can be electronically controlled through an electronic circuit and sensors mounted near the valves (402, 404).

The previously described versions of the subject matter and its equivalent thereof have many advantages, including those which are described below. The exhaust system described herein provides two modes of exhaust sound effect, thus preventing any unnecessary modifications of the vehicle. The exhaust system selectively switches between two passages for providing two modes of exhaust sound, i.e., a cruise mode sound and a racing mode sound, by using a simple mechanism, thereby eliminating the use of any complex mechanism, such as a gear mechanism. The elimination of the gear mechanism prevents the event of failure of gear meshing and avoiding undesirable sound effects. Also, such an exhaust system eliminates the use of dual exhaust pipes to provide two different sound characteristics, thereby eliminating additional cost of installing and maintaining two exhaust systems. Further, the exhaust system does not include any moving parts such as movable pipes or movable expansion chambers, thereby providing a stable flow of exhaust gases. Similar concepts/ features of the exhaust system described above may be employed to provide two or more exhaust sound modes.

The passages provided by the exhaust system as described herein can be effectively used for exhaust gases at all pressure, as only one passage remains open during various cycles of the IC engine. Additionally, the design and placement of expansion chambers in the muffler effectively reduces the high back pressure generated during the cruise mode, without affecting the performance of the IC engine.

The muffler of the exhaust system is designed such that minimum space is occupied on the frame structure of the vehicle, thereby reducing the manifesting and assembling cost of the exhaust system. The number of expansion chambers can be varied to vary the exhaust sound effect as per the need. The exhaust system can be used in any type of vehicle including two-wheelers, three-wheelers, four-wheelers, trucks, and busses.

While certain features of the claimed subject matter have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now occur to those skilled in the art. It is, therefore, to be understood that the appended claims

are intended to cover all such modifications and changes that fall within the true spirit of the claimed subject matter.