Catalytic converter mounting

Field of the invention

The present invention relates generally to an exhaust system for an internal combustion engine and more particularly pertains to a catalytic converter mounting in the exhaust system.

Background of the invention

The present invention relates to an exhaust system usually present in all internal combustion engine driven vehicles. Internal combustion engines operate by drawing power from a controlled explosion of air-fuel mixture within a combustion cylinder. In a typical four-stroke combustion cycle, an intake mixture of air and fuel is drawn into the combustion cylinder, compressed and ignited to produce power. The hot gases generated during combustion are finally shunted out of the combustion cylinder of the engine through the exhaust system.

Typically, an exhaust system comprises at least one conduit for transporting the exhaust gases from combustion cylinder of the engine to a remote discharge point i.e. the exhaust pipe. Moreover the exhaust system further includes at least one muffler or silencer at the rear end of the exhaust pipe. Additionally the exhaust system must reduce exhaust sound as much as possible. Hence preferably a muffler is fitted with a reasonably sized, easy to service, sound absorbing media to attenuate exhaust noise.

The exhaust gases moving out of engine contain unbumt or partially oxidized gases and particulate matter which need to be purified before being released to the atmosphere. For this purpose, a hot tube catalytic converter made of a perforated tube coated with noble metals on inner and outer diametrical surface is commonly used in the exhaust system through which exhaust gases are passed thereby purifying them.

Generally a hot tube catalytic converter is located in the exhaust gas flow direction in such a way that hot tube catalytic converter and hot tube catalytic converter cover are conjoint at the exhaust gas inlet side of the exhaust pipe. Due to Bernoulli's principle, exhaust gases pass through the hot tube catalytic converter at high velocity but at low pressure. Hence only a small volume of exhaust gases engage between the hot tube catalytic converter and the hot tube catalytic converter cover and this result in less interaction of a major portion of the exhaust gases with the outer diametrical surface of the hot tube catalytic converter.
Therefore the outer surface of the hot tube catalytic converter is not utilised completely to its potential and is under-efficient as the gases are not uniformly distributed over the surfaces of the hot tube catalytic converter while passing through it. The present invention is directed to overcoming one or more problems as set forth above.

Summary of the invention

It is hence an object of the present invention to provide an improved exhaust system comprising a catalytic converter arrangement that provides a uniform and better distribution of the exhaust gases over its surface area. Therefore the present invention, in accordance with an embodiment thereof, discloses an exhaust gas path construction for an exhaust system of an internal combustion engine comprising a hot tube catalytic converter, a hot tube catalytic converter cover, an exhaust gas inlet to said hot tube cover and an exhaust gas outlet from said hot tube cover, wherein the exhaust gases enter through exhaust gas inlet, expand in the hot tube cover and pass through the hot tube and exit through said exhaust gas outlet.

Another object of the present invention is to provide an improved catalytic converter arrangement so as to increase usage of the entire catalyst coating on both sides of the hot tube catalytic converter during engine operation without increase in cost and weight.

The foregoing objectives and summary provide only a brief introduction to the present invention. To fully appreciate these and other objects of the present invention as well as the invention itself, all of which will become apparent to those skilled in the art, the ensuing detailed description of the invention and the claims should be read in conjunction with the accompanying drawings. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent those skilled in the art from this detailed description.

Brief description of the drawings

Figure 1 shows a schematic view of the concerned two wheeled straddle type vehicle.

Figure 2 shows the improved exhaust gas path construction according to the present invention.

Detailed description of the invention

In the ensuing exemplary embodiments, the vehicle is a two wheeled motorcycle. However it is contemplated that the disclosure in the present invention may be applied to any automobile with an exhaust system without defeating the spirit of the invention.

Further "front" and "rear", and "left" and "right" referred to in the ensuing description for the illustrated embodiment refer to front and rear, and left and right directions as seen in a state of being seated on a seat of the motorcycle and looking forward. Furthermore, a longitudinal axis refers to a front to rear axis relative to the motorcycle, while a lateral axis refers generally to a side to side, or left to right axis relative to the motorcycle.

The present invention is now described in detail in connection with the rendered drawings. It should be noted that like elements are denoted by the same reference numerals throughout the description. The detailed explanation of the constitution of parts other than the invention which constitutes an essential part has been omitted at opportune places.

As shown in Figure 1, a typical motorcycle 1 comprises a body frame assembly made up of a number of tubes welded together. The motorcycle 1 has a steerable front wheel 11 and a driven rear wheel 12. The body frame primarily includes a head pipe 101, a main tube approximately horizontal to the ground and enclosed by various motorcycle components and a down tube 102. The head pipe 101 is disposed at a front end of the body frame of the motorcycle and a front fork 103 rotatably carries the front wheel 11. The front fork 103 may be connected to the head pipe 101 by any known type of suspension system. The head pipe 101 supports a steering shaft (not shown) disposed inside the head pipe 101. The upper and lower ends of the steering shaft are fixed on an upper bracket and the under bracket. The front end of the main tube and an upper end of the down tube 102 are connected to the head pipe 101. The down tube 102 extends obliquely downward in front of an internal combustion engine E from the head pipe 101 whereas the main tube extends rearward from the front end thereof.

The engine E is disposed below the main tube, and the main tube supports it. The engine may be an engine of a water-cooled type or air-cooled type. Drive force output from the engine is transmitted to the rear wheel 12 via a chain. A front fender 104 is provided below the under bracket to avoid the motorcycle and its occupants from being splashed with mud.

A fuel tank 105 is disposed above the main tube, on the upper side of the engine E, for storing the fuel for propelling the motorcycle 1. A seat 106 for a driver and a pillion is further provided, with the said seat being placed behind the fuel tank 105 and rearwardly of the main tube.

The rear wheel 12 revolves about a central axle 13. The axle 13 is supported at each end by a swing arm 14, the swing arm in turn pivotally connected to the body frame of the motorcycle by a rear shock absorber 300. Generally a motorcycle may use any of the two arrangements for rear shock absorbers, namely dual shock and mono shock. However the present invention is exemplified through a dual shock absorber. The dual shock absorbers are fixed at their upper ends to the motorcycle frame. Their lower ends are fixed to the swing arm 14.

The anterior portion of the motorcycle placed forward to the fuel tank 105 comprises of a headlamp assembly, the headlamp assembly further comprising a headlamp 108 and a visor 107. The handle bar assembly further comprises of a handle bar 110 extending transversely to the vehicle. The handle bar 110 is fixed on an upper bracket 111. A pair of rear view mirror 109 is mounted one each on either side of the handle bar by the use of brackets. A brake lever 112 is attached forwardly of the handle bar generally at the right side of the handle bar 110.

An exhaust system is usually present on the right side of the motorcycle originating from the internal combustion engine and spanning across the longitudinal axis of the motorcycle towards the rear. The present invention, in accordance with an embodiment thereof, describes an exhaust gas path construction 300 described in Figure 2 for the exhaust system of an internal combustion engine for efficient use of a hot tube catalytic converter present in the exhaust system.

The said exhaust system according to the present invention comprises a hot tube catalytic converter 302, a hot tube catalytic converter cover 301, an exhaust gas inlet 303 to said hot tube catalytic converter cover 301 and an exhaust gas outlet 304 from said hot tube catalytic converter cover 301, wherein the exhaust gases from the internal combustion engine enter through exhaust gas inlet 303, expand in the hot tube catalytic converter cover 301 and pass through the hot tube and exit through said exhaust gas outlet 304.

The hot tube catalytic converter 302 has a hot tube made of a perforated sheet coated with elements suitable for catalytic conversion of exhaust gases. The said coating is made of noble materials like Platinum, Palladium and Rhodium in required ratio present on both inner 305 and outer 306 diametrical surface of hot tube of the hot tube catalytic converter 302. This coating comes in contact with exhaust gases and works as catalyst to purify exhaust gases from the engine. More contact area of exhaust gases with the hot tube leads to more volume of exhaust gases being purified.

Therefore the exhaust gas path as disclosed in the present invention is such that the hot tube catalytic converter 302 is placed against the flow of exhaust gases on the opposite side of the exhaust gas inlet 303 and the gap between said hot tube catalytic converter 302 and said catalytic converter cover 301 is blocked at said exhaust gas outlet 304. The positioning of the hot tube catalytic converter 302 ensures that the exhaust gases coming into the hot tube catalytic converter cover 301 are uniformly distributed in the available space, both on the inner surface 305 and outer surface 306 of the hot tube catalytic converter 302.

When low pressure is created due to high velocity of exhaust gases through the hot tube catalytic converter 302, exhaust gases present in the gap between the hot tube catalytic converter cover 301 and hot tube catalytic converter 302 utilise the coating on the outer surface 306 of the hot tube catalytic converter 302 due to increased contact area and enter through the perforations on the hot tube catalytic converter 302 towards the exhaust gas outlet 304.

In the prior art, the coating on the outer diameter of the hot tube was not effectively utilized owing to high velocity of exhaust gases and positioning of the hot tube and the said gases used to interact mainly with the inner diameter of the hot tube. On the other hand, as a result of the present exhaust gas path construction, the catalytic conversion efficiency of the hot tube catalytic converter increases substantially. Therefore when the hot tube is placed in opposite to exhaust gas flow direction, then gas contact with hot tube increases as the gases come in contact with outer surface of hot tube thereby resulting in effective conversion of pollutants.

The present invention is thus described. The terms and expressions in this specification are of description and not of limitation and do not exclude any equivalents of the features illustrated and described, but it is understood that various other embodiments are also possible without departing from the scope and ambit of this Invention which will become apparent to those skilled in the art from this detailed description. Accordingly, the description is to be understood as an exemplary embodiment and reading of the invention is not intended to be taken restrictively.

We claim:

1. An exhaust gas path construction for an exhaust system of an internal combustion engine comprising;

a hot tube catalytic convertor;

a hot tube catalytic convertor cover;

an exhaust gas inlet to said hot tube catalytic convertor cover; and

an exhaust gas outlet from said hot tube catalytic convertor cover;

wherein the hot tube catalytic converter is positioned inside the hot tube catalytic convertor cover on the opposite side of the exhaust gas inlet in such a way that the exhaust gases from the said engine
enter through exhaust gas inlet, expand in the hot tube catalytic convertor cover, pass through the hot tube catalytic convertor cover and exit through said exhaust gas outlet.

2. The exhaust gas path construction as claimed in claim 1, wherein said hot tube catalytic convertor is a perforated sheet coated on both sides with elements suitable for catalytic conversion of exhaust gases.

3. The exhaust gas path construction as claimed in claim 1, wherein the gap between said hot tube catalytic convertor and said hot tube catalytic convertor cover is blocked at said exhaust pipe outlet side.

4. A motorcycle having said exhaust gas path construction as claimed in claim 1.

5. The exhaust gas path construction substantially as claimed in any of the preceding claims and illustrated with reference to the accompanying drawings.