TECHNICAL FIELD
[0001] The present subject matter relates generally to a two wheeled vehicle and more particularly to an exhaust device for it.
BACKGROUND
[0002] Generally, a two wheeled vehicle comprises of a frame assembly extending rearwardly from a head tube. The frame assembly acts as a skeleton and a structural member for the vehicle that supports the vehicle loads. A front wheel is connected to a front portion of the frame assembly through one or more front suspension(s). The frame assembly extends towards a rear portion of the vehicle. A rear wheel is connected to a frame assembly through one or more rear suspension(s). The frame assembly comprises of an engine assembly coupled to it. The engine assembly is functionally connected to the
rear wheel, which provides forward motion to the vehicle. A exhaust device is provided
at a lateral side of the vehicle mounted to the frame assembly or the vehicle through a mounting bracket. The exhaust device extends in a rearward direction along the length of the vehicle. An exhaust port is provided in the engine assembly through which an exhaust pipe extends in a reverse direction forming a part of the muffler assembly. .
[0003] Conventionally, in a two-wheeled vehicle the exhaust device is provided to reduce the toxicity of exhaust gases and to dampen the noise arising from the engine. The Exhaust device comprises of a catalytic converter which helps in oxidation of the carbon monoxides, unburnt hydrocarbons and NOx into harmless oxides which are ultimately released in the atmosphere. Generally a baffle assembly is provided in the exhaust system which helps in dampening the noise and provides a better sound quality.' It also helps in reducing the temperature of the exhaust gases being emitted. Furthermore, an exhaust system also adds to the aesthetic appeal of the two wheeled vehicle as well.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] The detailed description of the present subject matter is described with reference to the accompanying figures. Same numbers are used throughout the drawings to reference like features and components.

[0005] Fig. 1. illustrates the side view of a two-wheeled vehicle employing the embodiment of the present subject matter.
[0006] Fig. 2. illustrates the side view of the cut section of an internal combustion engine and the exhaust device according to the embodiment of the present subject matter.
[0007] Fig. 3. illustrates the cut sectional view of the exhaust device according to the embodiment of the present subject matter.
[0008] Fig. 4. illustrates the side cut section view of a exhaust pipe front portion according to the embodiment of the present subject matter.
[0009] Fig. 5. illustrates the side cut section close up view of a exhaust pipe front portion according to the embodiment of the present subject matter.
[00010] Fig. 6a. and Fig. 6b. illustrates the RPM v. torque and RPM v. Power illustrating the advantage of the exhaust device employing the embodiment of the present subject matter.
DETAILED DESCRIPTION
[00011] Typically, a two wheeled vehicle is operated through an internal combustion (1C) engine which is coupled to the frame assembly. Air fuel mixture is supplied to the IC engine by means of an intake system. Thereafter combustion of the air fuel mixture takes place so that a piston disposed in the IC engine is set into motion. The piston is operated in a linear motion, after which said liner motion is converted to a rotational motion, wherein said rotational motion is transferred to the rear wheel finally resulting into motion of the vehicle. This mechanism also results in generation of power and torque by the IC engine.
[00012] An IC engine which is operated using hydrocarbon fuel produces power by combustion of the fuel and air to provide motive force to the vehicle. The IC engine comprises of a cylinder head, a reciprocating piston inside a cylinder block located below the cylinder head, a rotatable crankshaft to transfer mechanical energy to the transmission system and a connecting rod transferring energy imparted to the reciprocating piston to the rotatable crankshaft. During operation of the IC engine, the burning of air fuel

mixture occurs in a combustion chamber interposed between the cylinder head and cylinder block. The exhaust gases produced after combustion is expelled from the 1C engine through an exhaust port which facilitates the movement of the exhaust gases to an exhaust device. The exhaust device extends rearward ly. along the length of the vehicle towards any one side. The unburnt hydrocarbons in the exhaust gases is oxidized as it passes through the catalytic converter and there is reduction in noise as it passes through the muffler assembly and is later released in the atmosphere. Typically, the exhaust gases enter the exhaust device through an exhaust pipe front portion after which it passes through the catalytic converter for conversion, and finally enter the baffle assembly. In the baffle assembly the gases, pass through a bend pipe and are released through a set of perpetrating holes formed at its end. The gases finally enter a baffle pipe before being emitted into the atmosphere through a tail pipe. This whole process provides a better diffusion of the gases so that the noise is dampened and a better sound quality is ■provided. The current" process also'helps in reduction of • temperature'~of gases. Additionally the exhaust device also adds to the aesthetics and aerodynamics features of the vehicle.
[00013] The IC engine operates either in two cycles or four cycles, wherein the last cycle is the exhaust stroke, in which the reciprocating piston moves towards the top dead centre from the bottom dead centre and an exhaust valve is open during which the high pressure exhaust gases are expelled. At one point, the intake valve is opened to expel the exhaust ■ gases using the incoming fresh air-fuel mixture. The point at which both the intake valve and the exhaust valve is open is referred to as valve overlap. When high pressure exhaust gases are expelled into the exhaust manifold, the exhaust gases come in the form of an exhaust pulse due to the large pressure difference between the exhaust gases in the combustion chamber and the pressure outside the exhaust port. This exhaust pulses travel in the form of wave and have properties of waves. During the travel of the exhaust gases in the exhaust pipe front portion any sudden change in dimension causes a compression wave or a negative pressure wave, which reflects back in the opposite direction to that of the exhaust gas. These reflected exhaust waves can be made to work in such a manner as to assist the scavenging the combustion chamber by permitting it inside and help draw fresh fuel charge into the cylinder,'improving power and fuel efficiency.. This reflected exhaust

wave enters the.combustion chamber during valve overlap and resulting effective removal of exhaust gases from the combustion chamber, thereby boosting the performance. The performance of the engine depends upon the traveling of exhaust waves in the exhaust system. The wave variations can be controlled by changing the various aspects of the exhaust muffler device.
[00014] For a given engine specifications like displacement volume, maximum torque, maximum power, volumetric efficiency, etc., the exhaust system can be used as the tunable parameter to achieve the target specifications. In such a case, the exhaust pipe length and diameter plays a vital role in optimizing the engine performance. The length and diameter of exhaust pipe is determined based on the engine valve timing and displacement volume of the engine. The exhaust pipe usually has one inner pipe portion and an outer pipe portion. The inner pipe portion extends from the entry of the gases in the exhaust port till the perforated pipe, and the outer pipe portion is from the entry of the gases in the exhaust port to the muffler unit. Generally in prior art, the diameter of the inner pipe portion is increased at the very end downstream and the outer pipe portion is enlarged by predetermined length from the enlarged diameter portion of inner pipe portion. By doing so, the pulsation effect intensity (reflected exhaust waves) will be very less, as the enlarged portion is smaller in length and this arrangement will have very minimal benefit in engine performance. The above explained phenomenon is said to happen only at one particular frequency of operation. That frequency can be target maximum torque rpm. The design parameter that controls the engine performance is length ratio of the exhaust pipe, diameter ratio of the exhaust pipe. These two ratios are determined to ensure maximum scavenging benefit is obtained by the reflected exhaust waves.
[00015] Hence, it is the principal object of the present subject matter is to provide an exhaust muffler device suitably designed to create reflected exhaust waves, and utilize the same for effective scavenging of the combustion chamber.
[00016] Another object of present subject matter, is that the exhaust system should generate reflected exhaust waves exactly during valve overlap in the combustion chamber.

[00017] Another object of the present subject matter, is for reducing defects during welding of the inner tube portion to the perforated tube portion.
[00018] With the above design changes, the following advantages can be obtained such as improved engine performance especially the power and torque output, minimal changes to existing layout, reduced fuel consumption and improvement of efficiency.
[00019] The present invention along with all the accompanying embodiments and their other advantages would be described in greater detail in conjunction with the figures in the following paragraphs.
[00020] Fig. 1. illustrates a right side view of a saddle-ride type vehicle (100) colloquially called a motorcycle, in accordance with an embodiment of the present subject matter. In an embodiment, the saddle-ride type vehicle (100) of the present subject matter includes an internal combustion (IC) engine (101). The vehicle further • includes a front wheel-(110), a rear wheel (103),- a body frame, a fuel tank (107) and seat- •• (106). The Body frame includes a head pipe (111), a main tube (112), a down tube (113), a pair of seat supporting structures (117) and seat rails (not shown) disposed between the pair of seat supporting structures. The head pipe (111) supports a steering shaft (121) with two brackets - upper bracket (not shown) and lower bracket (120) at each end. Two telescopic front suspension (114) (only one shown) is attached to the lower bracket (120) on which is supported the front wheel (110). The upper portion of the front wheel (110) is covered by a front fender (115) mounted to the lower portion of a front fork of the telescopic front suspension (114). A handlebar assembly (108) is fixed to upper bracket and can rotate to both sides. A headlamp assembly (109) is disposed in the front portion of the headtube (111). An exhaust assembly (200) is attached to the IC engine (101) at a front end of the IC engine (101) and extends rearwards from one side of the two wheeled vehicle in the opposite direction of the chain (in the present embodiment, the exhaust assembly is disposed towards the right side of the vehicle in the width direction). Down tube (113) is disposed in front of the IC engine (101) and stretches slantingly downward from head pipe (111). A bracket (116) is provided at the lower end of down tube (113) for supporting the IC engine (101) on the down tube (113) disposed on substantially front portion of the two wheeled vehicle. Main tube (112) is located above the IC engine (101)

and stretches rearward from head pipe (111) and connects to the rear of the IC engine (101). The seat supporting structure (117) is joined to the rear end of the main tube (112) and stretches rearward. The seat rails, which are joined to the main tube (112) and stretching rearward to support a seat assembly (106) disposed above these seat rails. Left and right rear swing arm bracket portions (not shown) support a rear swing arm (not shown) to swing vertically, and a rear wheel (103) is connected to rear end of the rear swing arm. Generally, two rear wheel suspensions (102) (only one shown) are arranged between rear swing arm. A tail lamp assembly (104) is disposed on the rear end of the seat (117). A grab rail (105) is also provided on the rear of the seat supporting structure (117). Rear wheel (103) is arranged below seat assembly (106) and rotates by the driving force of the IC engine (101) transmitted through a chain drive (118) from the IC engine (101). A rear fender (122) is disposed above the rear wheel (122) and attached to the seat supporting structures (117).
[00021] Fig. 2. illustrates a side view of the cut section of the IC engine and the exhaust assembly connected to it according to the embodiment of the present invention. The IC engine (101) is made up of a cylinder head (201), cylinder block (202) and crankcase (203). The IC engine (101) also comprises of a magneto assembly (not shown) which functions as a magneto coil assembly during operation to recharge a battery. The IC engine (101) also has a. sprocket (not shown) disposed outside of thecrankcase (203) and is capable of rotation when the IC engine (101) is in operation. The IC engine (101) also comprises a kick-starter system which when actuated by the kick-lever (211) helps in cranking the IC engine (101) during start. The IC engine (101) comprises a reciprocating piston (251) enclosed in the cylinder block (204), a connecting rod (206) connecting the reciprocating piston (251) to a rotatable crankshaft (252). During operation, the burning of fuel and oxidizer occurs in a combustion chamber (207) and transfers mechanical energy to the reciprocating piston (204) which transfers the mechanical energy to the rotatable crankshaft (252) which generates power due to the slider crank mechanism. In the embodiment of the present invention, the engine operates in four cycles namely, intake stroke, compression stroke, power, and exhaust stroke. Combustion of air fuel mixture occurs at the end of compression stroke and beginning of power stroke, after combustion the hot exhaust gases are generated which are expelled out of the cylinder

block during the exhaust stroke to an exhaust port (203a) and is passes to the exhaust device (200).
[00022] Fig. 3. illustrates the cut sectional view of the exhaust device according to the embodiment of the present subject matter. The exhaust muffler device (200) comprises an exhaust pipe front portion (201) which is connected to the exhaust port (203a) and extends rearwards, and a muffler unit (212) which is connected to the exhaust pipe front portion (200) and exhausts the high-temperature and high-pressure gases passing through the exhaust muffler device to the outside atmosphere which reducing the pressure and noise of the exhaust gases. There is a catalytic converter unit (305) connected to the exhaust pipe front portion (200) at the end wherein it joins the muffler unit (213). The end portion of the exhaust pipe front portion projects inwards in the catalytic converter unit (305) and comprises a perforated tube (304) with plurality of perpetrating holes at its end from where the gases are released after passing through it. The exhaust pipe front portion (201) is essentially made up of two pipes, one within the other. An inner pipe portion (301) and the outlet pipe portion (201a). The exhaust pipe front portion (201) has a mounting flange (201b) at one end for mounting to the cylinder head (203) of the 1C engine (101).
[00023] As seen in the image below the perforated holes (304) in the pipe is welded to the inner pipe portion (301) of the exhaust pipe front portion (201). During the bending operation of the exhaust pipe front portion (201) in pipe design, the insertion of the inner pipe portion (301) onto the outer pipe portion (201a) will be difficult as the annular gap between the inner pipe and the outer pipe is small. The weld bead joining the inner pipe portion (301) and the perforated pipe (304) reduces the annular gap between the tubes at that zone. During manufacturing of the exhaust pipe front portion (201), as a part of the manufacturing process, the gap is filled with shots of very small diameter and rammed between the annular gap of the pipes. This is to reduce the wrinkle formation and to achieve defect less bend. As the annular gap is too small, the filling and ramming of shots inside the gap cannot be achieved properly which results in defective bends and more rejection of parts. In order to avoid the defects in this process, the attachment of the exhaust pipe front portion (201) is modified in such a way that the perforated tube (304) is welded to the inner pipe portion (301) which is protruded out from the outer pipe

portion (201a). By doing so, the perorated tube (304) can be welded on the protruded region of inner pipe portion (301) after the bending process. Thereby reducing the defects in the process.
[00024] The catalytic converter unit (305) is reduces the harmful carbon monoxide and uriburnt hydrocarbons in the exhaust gas to carbon dioxides by catalyzing it by a redox reaction. The catalytic converter unit uses rare earth metals such as platinum as a catalyst to convert the exhaust gases. The catalyst is arranged in the form of dense honeycomb structure so that the exhaust gases- touch a bigger area of catalyst so that they are converted more quickly and efficiently. From the catalytic converter unit (305) the exhaust gases enter the muffler unit (213). The muffler unit (213) is designed to reduce the noise due to sound pressure created by the IC engine on the exhaust gases by way of acoustic quieting. The emitted noise is 'muffled' by a series of resonating chambers (307) lined with insulation harmonically tuned to cause destructive interference, wherein opposite sound waves cancel each other out. The series of resonating chambers (307) provides sufficient volume and time for diffusion of the exhaust gases resulting in better sound quality and decreased temperature. The exhaust gas is finally made to exit through a tail pipe (214) to the atmosphere.
[00025] Fig. 4. illustrates the side cut section view of a exhaust pipe front portion according to the embodiment of the present subject matter. As described, the exhaust device (200) comprises of the exhaust pipe front portion (201) connected to the exhaust port (203a) of the internal combustion engine (101). The exhaust pipe front portion (201) is bent to have two corners and comprises an outer pipe portion (201a) extending from the exhaust port (203a) to the muffler unit (212), an inner pipe portion (301) disposed annularly within the outer pipe portion (201a). The downstream end of the inner pipe portion (301) is flared to increase in diameter as compared to the upstream .end (301) to obtain a zone of area change (303), said zone of area change (303) enabling the reflection of the exhaust wave pulsations to assist in scavenging the combustion chamber (207) of the IC engine (101). Further, the ratio of the total axial length in unbent orientation (L|) measured along an axis of the inner pipe portion upstream end (301) and the total length (L2) measured along an axis of the inner pipe portion downstream end (302) is set to a first predetermined value, and the ratio of the diameter of the inner pipe portion

downstream end (D2) and the diameter of the inner pipe portion upstream end (Di) is set to a second predetermined value. The dimensions of the various parameters such as total axial length in unbent orientation (Li), the total length (L2), diameter of the inner pipe portion upstream end (Di), and diameter of the inner pipe portion downstream end (D2) depends on the cubic capacity of the IC engine (101). But in order for effective scavenging due to reflection of the exhaust wave pulsations, the ratio of total length in unbent orientation (Li) and the total length (L2) must be fixed. The zone of area change (303) is disposed on the unbent horizontal portion substantially downstream of the exhaust pipe front portion (201). As seen in Fig. 2, after reflection, the reflected exhaust wave pulsations (210) reflected back to the combustion chamber (207) of the IC engine (101).
[00026] Further, the ratio of the diameter of the inner pipe portion downstream end (D2) • to the diameter of the inner pipe portion upstream end (D|) is also fixed. In the one embodiment, the first predetermined value is in a range of 3 to 4. The second predetermined value is in a range of 1 to 2. In another embodiment, for a 150 cubic capacity of the IC engine, the first predetermined value is 3.72 and the second predetermined value is 1.12.
[00027] Fig. 5. illustrates the side cut section close up view of'a exhaust pipe front portion according to the embodiment of the present subject matter. The downstream end of the inner pipe portion (302) is flared to be of increased diameter as compared to the upstream end (301). The zone of area change (303) is gently curved to provide for gradual area change. Further, as explained above the inner pipe portion (302) is projected outward towards the interior parts of the muffler (212).
[00028] Fig. 6a. and Fig. 6b. illustrates the RPM v. torque and RPM v. Power illustrating the advantage of the exhaust device (200) employing the embodiment of the present subject matter. During scavenging the left over exhaust gases are removed during valve overlap. This process directly improves the performance of the IC engine. As seen from the graph, fairly higher torque output is obtained from the IC engine (101) for the same revolutions per minute as compared to prior art engines of the same capacity. The power output is also improved as seen in Fig. 6b. The results as illustrated in Fig. 6a. and

Fig. 6b. illustrates the improvement in performance when the ratio of the total axial length in unbent orientation (Li) measured along an axis of the inner pipe portion upstream end (301) and the total length (L2) measured along an axis of the inner pipe portion downstream end (302) is set to a first predetermined value, and the ratio of the diameter of the inner pipe portion downstream end (D2) and the diameter of the inner pipe portion upstream end (D|) is set to a second predetermined value.
[00029] Many modifications and variations of the present subject matter are possible in the light of above disclosure. Therefore, within the scope of claims of the present subject matter, the present disclosure may be practiced other than as specifically described.

1. An exhaust muffler device (200) for an internal combustion engine (101) comprising:
an exhaust pipe front portion (201) connected to an exhaust port (203a) of the internal combustion engine (101), said exhaust pipe front portion (201) bent to have two corners;
comprising:
an outer pipe portion (201a) extending from the exhaust port (203a) to the muffler unit (212);
an inner pipe portion (301) disposed annularly within the outer pipe portion (201a);
wherein, •
the downstream end of the inner pipe portion (302) is flared to increase in diameter as compared to the upstream end (301) to obtain a zone of area change (303), said zone of area change (303) enabling the reflection of the exhaust wave pulsations to assist in scavenging a combustion chamber (207) of the internal combustion engine (101); and
wherein the ratio of the total axial length (Lj) measured along an axis of the inner pipe portion upstream end (302) and the total length measured along an axis of the inner pipe portion downstream.end (L2) is set to a first predetermined value.
2. The exhaust muffler device (200) as claimed in claim 1, wherein the first predetermined value is in a range of 3 to 4.
3. The exhaust muffler device (200) as claimed in claim 1, wherein the ratio of the diameter of the inner pipe portion downstream end (D2) and the diameter of the inner pipe portion upstream end (Di) is set to a second predetermined value.

4. The exhaust muffler device (200) as claimed in claim 3, wherein the second predetermined value is in a range of 1 to 2.
5. The exhaust muffler device (200) as claimed in claim 1, wherein the zone of area change (303) is disposed on the unbent horizontal portion substantially downstream of the exhaust pipe front portion (201).
6. The exhaust muffler device (200) as claimed in claim 1, wherein the exhaust muffler device further comprises:
a catalytic converter (305) to purify exhaust gases;
a perforated tube (304) attached to the end of the .exhaust,pipe front portion (201) to diffuse gases into a catalytic converter (305);
and wherein the inner pipe portion (301) having the flared portion (302) extends beyond the outer pipe portion (201a) at the junction of the exhaust pipe front portion (201) and the muffler unit (212) to hold the perforated tube (304) to diffuse gases into a catalytic converter (305).
7. The exhaust jnuffler device (200) as claimed in claim 1, wherein the zone of area change (303) is gently curved to provide for gradual area change. .
8. The exhaust muffler device (200) as claimed in claim 1, wherein the internal combustion engine (101) is in the range of 150 cubic capacity.
9. A two wheeled vehicle (100) comprising the exhaust muffler device (200) as claimed in any of the preceding claims.