Exhaust System for an Internal Combustion Engine

Field of the Invention

The present invention relates to an exhaust system and more particularly to an exhaust system for an opposed piston internal combustion engine.

Background of the Invention

Conventional internal combustion engines used in two wheeled vehicles usually have the combustion chamber formed between a cylinder head and a top surface of a piston reciprocating in a cylinder bore. The compression ratio which is one of the factors that influences the power generated by such an engine is limited due to the inherent structure of the engine. For example, the compression ratio is limited because of the shape of the cylinder head forming the combustion chamber.

To increase the compression ratio and consequently the power generated, engines have been developed that have opposed pistons in the respective cylinder bores. The pistons in the two bores are connected to separate crankshafts at the far ends i.e. near bottom extreme positions of the cylinder bore. The power from one crankshaft is added to the power of the other crankshaft by using a crank train assembly, disposed on one side of the engine.

The packaging of such engines is usually done in such a way that a central axis of the engine is approximately parallel to a central axis of the vehicle, for example, a two-wheeler. As a result of such packaging, the engine oil is not capable of flowing under the effect of gravity and requires a separate pump for lubricating and cooling the different parts of the engine. Further, due to the aforementioned packaging and orientation of the engine in the vehicle, stagnation of oil takes place at the bottom of the piston and some oil may also seep into the combustion chamber when the vehicle is parked for long durations. As a result of the seepage, the lubricating oil may undergo combustion during operation of the engine. Hence, the emissions from the engine may not satisfy the various norms and policies related to pollution control.

To overcome the above problems associated with the conventional opposed piston engine, embodiments of an inclined bore opposed piston internal combustion engine were disclosed in Indian Patent Application 1296/CHE/2011. As a result of the inclined cylinder bores of the engine, the distance between centres of the first crankshaft and the second crankshaft is reduced, and the overall length of the engine is less than the overall length of a conventional opposed piston engine of equivalent capacity. The reduction in the size of the engine helps reduce the inertia of the engine and assists in easy packaging of the engine on body of the vehicle, for example, a two-wheeled vehicle. In addition, the incline between the cylinder bores of the engine allows quick drainage of oil into an oil sump and reduces seepage of oil into the combustion chamber of the engine when the vehicle is parked and avoids oil accumulation behind the operative piston. The combustion chamber hence formed is compact in size.

In the aforementioned engine and other known internal combustion engines, the exhaust port is located downwards as shown in Figure 1 due to which the ground clearance between the exhaust pipe and the ground is significantly less. This results in damage to the exhaust pipe and muffler body due to collision with stones, rocks and uneven hard surfaces. Moreover, in these engines, hot gas effect i.e. tendency of the hot gases to move up is not utilised to the optimum potential as the exhaust gases are forced to move a certain path opposed to their natural direction of flow.
As a result of the said construction, there is considerable pumping loss to force the exhaust gases along the exhaust pipe. The pumping loss can be reduced by increasing the diameter of the exhaust port but that will lead to a significant dip in the engine performance. Another lacuna in the current state of art is the proximity of the exhaust pipe with the crankcase having engine oil reservoir causing oil temperature increase in the engine. The present invention is directed to overcoming one or more problems as set forth above.

Therefore, it is an object of the present invention to reduce pumping losses from the combustion chamber of an internal combustion engine considerably by orienting the intake and exhaust port.
Another aspect of the present invention is to provide an exhaust path construction that provides high ground clearance.

SUMMARY OF THE INVENTION

The subject matter described herein is applicable to a four stroke internal combustion engine and relates to an exhaust path construction provided from the radial exhaust valve such that the exhaust gases move in an exhaust pipe in a substantially upward direction passing through the muffler, the muffler being positioned opposed to gear train connection side.

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

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

Figure 1 illustrates layout of various known engines wherein the exhaust port is located downwards.

Figure 2 illustrates a schematic sectional view of an inclined bore internal combustion engine according to an embodiment of the present subject matter.

Figure 3 depicts a prospective view of the inclined bore internal combustion engine according to an embodiment of the present subject matter.

Figure 4 shows a sectional view of the inclined bore internal combustion engine according to an embodiment of the present subject matter.

Figure 5 illustrates a side sectional view of the inclined bore internal combustion engine according to an embodiment of the present subject matter.

Figure 6 shows a scooter type motorcycle on which the aforementioned inclined bore internal combustion engine is mounted.

DETAILED DESCRIPTION OF THE INVENTION

The subject matter described herein relates to the exhaust port orientation in an inclined bore opposed piston internal combustion engine. Various other features of the exhaust system proposed here will be discernible from the following further description thereof set out hereunder. In the ensuing description, 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.

Figure 2 illustrates a sectional view of an inclined bore internal combustion (IC) engine 100, according to an embodiment of the present subject matter. According to said embodiment, Figure 2 shows a longitudinal section of the inclined bore opposed piston IC engine 100, hereinafter referred to as engine 100.

In an embodiment, the engine 100 includes a cylinder block 102 (partially shown in figure) having a first cylinder bore 104, a second cylinder bore 106. In said embodiment, the cylinder block further includes a centre piece 108. In one embodiment, the cylinder block 102 is formed as a single component having the first cylinder bore 104, the second cylinder bore 106, and the centre piece 108. In another embodiment, the cylinder block 102 is formed as a plurality of cylinder block portions, each cylinder block portion having a cylinder bore 104, 106 formed therein. In said embodiment, the centre piece 108 is positioned between the cylinder block portions.

According to an aspect of the subject matter, the first cylinder bore 104 and the second cylinder bore 106 are inclined to each other. In one example, a first cylinder bore axis 110 and a second cylinder bore axis 112 are inclined to each other, such that an included angle a between the two axes 110 and 112 is less than 180°. In an embodiment, the included angle a is about 160°. The included angle can be understood as an angle formed between the first cylinder bore axis 110 and the second cylinder bore axis 112, measured from the first cylinder bore axis 110 in a counter¬clockwise direction. In said example, the first cylinder bore axis 110 and the second cylinder bore axis 112 can be understood as the central axes of the first cylinder bore 104 and the second cylinder bore 106, respectively. Further, in one embodiment, the centre piece 108, provided between the first cylinder bore 104 and the second cylinder bore 106, is formed as a hollow cylinder. Further, in said embodiment, the end surfaces of the centre piece 108 are inclined to each other at an angle of 180-a. The end surfaces of the centre piece 108 can be understood as the surfaces of the centre piece adjoining the first cylinder bore 104 and the second cylinder bore 106, respectively.

Further, at a bottom extreme end of the first cylinder bore 104, a first crankcase (not shown in the figure) is provided. The first crankcase houses a first crankshaft 114, which is connected to a first piston 116, reciprocating in the first cylinder bore 104, through a first connecting rod 118. Similarly, a second crankcase (not shown in figure) is provided at a bottom extreme end of the second cylinder bore 106. A second crankshaft 120 is disposed in the second crankcase, and is connected to a second piston 122 through a second connecting rod 124. The second piston 122 reciprocates in the second cylinder bore 106.

In addition, a first sleeve 126 and a second sleeve 128 are disposed in the first cylinder bore 104 and in the second cylinder bore 106, respectively. The sleeves 126, 128 may serve as a liner for the first cylinder bore 104 and the second cylinder bore 106, respectively. In an embodiment, the first sleeve 126 and the second sleeve 128 are disposed in the respective cylinder bore 104, 106 such that the sleeve 126, 128 is capable of sliding in the respective cylinder bore 104, 106 along a direction of the cylinder bore axis 110, 112. In an embodiment, the engine 100 includes a first actuator assembly 130 (partially shown in figure) and a second actuator assembly 132 (partially shown in figure) to actuate the first sleeve 126 and the second sleeve 128, respectively.

Further, in an embodiment, the first actuator assembly 130 includes a first rocker arm assembly and a first cam (not shown in figure). In said embodiment, the first cam is mounted on a first camshaft 134. Further, a first gear train 136 is coupled to the first camshaft 134 and provides a drive to the first camshaft 134, and hence, to the first cam. In one example, the first gear train 136 is further coupled to the first crankshaft 114 to provide the drive to the first camshaft 134. In an embodiment, the first crankshaft 114 may have a first crankshaft gear 138, which meshes with the first gear train 136. In another embodiment, the first crankshaft 114 can directly mesh with the first gear train 136. Further, the first camshaft 134 drives the first cam, which actuates the first rocker arm. In return, the first rocker arm actuates the first sleeve 126 in the first cylinder bore 104.

In an embodiment, the first sleeve 126 is provided with one or more inlet apertures (not shown in figure) for allowing charge to be inducted into the first cylinder bore 104. Further, the cylinder block 102 includes one or more inlet ports 140 that are connected to a fuelling system (not shown in figure) of the engine 100. For example, the fuelling system may include a carburettor or a fuel injection system. The actuation of the first sleeve 126 by the first actuator assembly 130 regulates an opening and closing of the inlet ports 140. In said embodiment, the first actuator assembly 130 actuates the first sleeve 126 to align the inlet apertures in the first sleeve 126 with the inlet ports 140 to open the inlet ports 140 and allow entry of charge into the first cylinder bore 126. In one embodiment, the first sleeve 126 is spring loaded on one end to keep the inlet ports 140 closed, until the first sleeve 126 is actuated to open the inlet ports 140.

In a similar manner as described above, the second actuator assembly 132 achieves the actuation of the second sleeve 128. In an embodiment, the second actuator assembly 132 includes a second rocker arm assembly and a second cam (not shown in figure). The second cam is mounted on a second camshaft 142, which, in one embodiment, obtains a drive from the first crankshaft 114 through the first gear train 136 and a second gear train 144. In another embodiment, the second camshaft 142 obtains a drive from the second crankshaft 120. In one implementation, a second crankshaft gear 146 meshes with the second gear train 144 and provides the drive to the second camshaft 142. In another implementation, the second crankshaft 120 directly meshes with the second camshaft 142 and provides the drive to the second camshaft 142.

In one embodiment, the second sleeve 128 includes one or more exhaust apertures (not shown in figure), that align with one or more exhaust ports 148 in the cylinder block 102 to open the exhaust ports 148 and to allow combustion products in the second cylinder bore 106 to escape. The alignment of the exhaust apertures in the second sleeve 128 and the exhaust ports 148 is achieved by the second actuator assembly 132, in the same manner as described with reference to the first sleeve 126.

The provision of the first actuator assembly 130 including the first gear train 136 and the provision of the second actuator assembly 132 including the second gear train 144 provides smooth and substantially noise-less operation of the engine 100. Further, such provision helps in achieving light weight and a compact layout of the engine 100.

In another embodiment, the first actuator assembly 130 and the second actuator assembly 132 can include electromagnetic actuators. In other embodiments, the actuator assemblies 130 and 132 can include other types of actuators, such as rack and pinion-type actuators.

Further, in one embodiment, the first crankshaft 114 meshes with the second crankshaft 120. In said embodiment, the first crankshaft 114 and the second crankshaft 120 are coupled to each other through the first gear train 130 and the second gear train 132, as is shown in Fig. 1. In an embodiment, the engine 100 is mounted on a body of a vehicle such that the first gear train 136 and the second gear train 144 are disposed such that the axes of the first gear train 136 and the second gear train 144 is below the first cylinder bore axis 110 and the second cylinder bore axis 112. With such a positioning of the first gear train 136 and the second gear train 144, the centre of gravity of the engine 100 is low and is close to a surface on which the vehicle runs. As a result of the low centre of gravity of the engine 100, the stability of the vehicle during operation is improved.

In an embodiment, a first crank offset is provided between the first piston 116 and the first crankshaft 114 and a second crank offset is provided between the second piston 122 and the second crankshaft 120. The provision of the crank offset between the piston 116, 122 and the crankshaft 114, 120 reduces load on joints between the piston 116, 122, the connecting rod 118, 124, and the crankshaft 114, 120. The reduction of load on the joints further decreases loss of power generated by the engine 100 at the joints. Further, the provision of the crank offset reduces oil churning in the engine 100. Further, the first crank offset and the second crank offset are provided in such a way that the first crankshaft 114 rotates in a direction opposite to the direction of rotation of the second crankshaft 120. The opposite directions of rotation of the first crankshaft 114 and the second crankshaft 120 reduce vibrations of the engine 100 and improve ride quality of the vehicle on which the engine 100 is mounted.

In addition, according to an embodiment, a first concave profile 150 is provided on a top surface of the first piston 116 and, similarly, a second concave profile 152 is provided on a top surface of the second piston 122. During operation of the engine 100, the top surface of the first piston 116 and the top surface of the second piston 122 are adjacent to each other at end of compression of charge, as shown in Fig. 1. In such a position of the pistons 116 and 122, the first concave profile 150 and the second concave profile 152 form a combustion chamber 154 therebetween, along with inner lateral wall of the centre piece 108. In an implementation, the combustion chamber 154, when formed, includes compressed charge. In another embodiment, the concave profile 150, 152 can be provided on the top surface of either the first piston 116 or of the second piston 122 to form the combustion chamber 154 between the top surfaces of the first piston 116 and the second piston 122.

In an embodiment, the combustion chamber 154 formed between the first piston 116 and the second piston 122 is hemispherical and formed as a bowl-shaped combustion chamber. In another embodiment, the combustion chamber 154 is formed in the shape of a sphere. It will be understood that, in other embodiments, the combustion chamber 154 can be formed in other shapes, such as oval, conical, pent-roof. An ignition element 156 is provided in the combustion chamber 154 to achieve combustion of the compressed charge in the combustion chamber 154. In one example, in case of a spark ignition engine, the ignition element 156 can be a spark plug, whereas in case of a compression ignition engine, the ignition element 156 can be a glow plug. In an embodiment, the ignition element 156 is disposed in a through-opening in a lateral wall of the centre piece 108. In said embodiment, the ignition element 156 is disposed in the combustion chamber 154 in such a way that substantially complete combustion of the charge can be achieved in the combustion chamber 154. In another embodiment, the engine 100 can include more than one ignition elements 156 disposed in the combustion chamber 154. It will be understood that, in other embodiments, a number of ignition elements 156 can be provided in the combustion chamber 154, so as to achieve a substantially complete combustion of the charge in the combustion chamber 154.

The engine 100 further includes an oil pump (not shown in figure) for supplying oil to various parts of the engine 100, for example, the cylinder block 102, the first crankshaft 114, and the second crankshaft 120. The oil pump may provide the oil to the various parts of the engine 100 for the purpose of lubrication and cooling of the parts. In one embodiment, the oil pump is mounted on a bottom side of the cylinder block 102, with reference to the mounting of the engine 100 on the vehicle, and obtains a drive from either one of the first crankshaft 114 and the second crankshaft 120. In said embodiment, an oil sump (not shown in figure) is formed at the bottom side of the cylinder block 102 for the accumulation of the oil. The provision of the oil pump and the oil sump at a bottom side of the cylinder block 102 of the engine 100 ensures adequate supply to the various parts of the engine 100 even at low oil level in the oil sump.

Figure 3 illustrates a prospective view of the said inclined bore internal combustion engine wherein an intake port 201 is located on the upper surface of the said engine so that the intake charge movement is along the gravity. The intake port 201 defines the intake charge path through which the incoming air-fuel mixture (also known as charge) enters the engine. This air-fuel mixture is then compressed and ignited in the said combustion chamber 154 thus driving the respective crankshafts. The exhaust gases formed as a product of the combustion then move out of the combustion chamber through an exhaust port 202 located in radial direction and approximately upwards in the engine. The exhaust port 202 is disposed approximately angular to the intake port 201 and both are in the same plane. According to a preferred embodiment of the present invention, the exhaust port can be disposed angularly with respect to the intake port, the said angle ranging from zero to ninety degrees with respect to the normal. Figure 4, 5 shows the sectional view of the said engine with the position of the respective intake and exhaust port.
Figure 6 illustrates the right side view of an embodiment of the present invention mounted on a vehicle, for example, a scooter type motorcycle. The exhaust port 202 being approximately laterally positioned, allows the hot exhaust gases to flow in their natural direction using the hot gas effect and then follow the exhaust pipe 203 thereafter finally moving out of the exhaust system through a muffler 204. The exhaust port, exhaust pipe and muffler together define the exhaust path followed by the exhaust gases to move out of the combustion chamber. The exhaust pipe 203 is also in the lateral direction rather than the conventional initially downward direction. The said engine 100 is disposed on the frame 300 of the exemplary vehicle and mounted using known mechanisms.

It will be appreciated that the present subject matter and its equivalent thereof offer many advantages, including those which are described henceforth. Exhaust gases have a tendency to move upwards and the exhaust port orientation in radially upward direction in the present invention allows them to flow in their natural direction thereby reducing the pumping loss. As a result of the lateral location of the exhaust port and the exhaust pipe, the ground clearance of the exhaust system increases sufficiently thereby saving the exhaust system from collision with stones, rocks and uneven hard surfaces when the vehicle is in moving condition. Moreover, as a result of this construction, pumping loss decreases considerably and overall efficiency of the engine increases.

The present invention is thus described. The said engine and its exhaust and intake system can be used in any of the vehicles including a motorcycle, a scooter type motorcycle or a moped. 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, modifications, substitutions, changes and equivalents are also possible without departing from the scope and ambit of the present invention which will now 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 system for a four stroke internal combustion engine comprising; an intake port defining an intake path to said internal combustion engine, a radial exhaust port defining an exhaust path from said internal combustion engine, a muffler assembly, a gear train assembly,

wherein an exhaust path construction is provided from the said radial exhaust port such that the exhaust gases move in a substantially upward direction inside the muffler.

2. The exhaust system for an internal combustion engine as claimed in claim 1, wherein said muffler is positioned opposed to gear train connection side.

3. The exhaust system for an internal combustion engine as claimed in claim 1, wherein the internal combustion engine is of opposed piston type.

4. An intake and exhaust system for an opposed piston twin cylinder four stroke internal combustion engine comprising:

an internal combustion engine fitted to a vehicle, an intake port to said internal combustion engine defining an intake path, an exhaust port from said internal combustion engine defining an exhaust path, wherein said intake path is oriented such that the incoming air to said engine follows a path defined by gravity; and

wherein said exhaust path from said internal combustion engine is oriented such that the exhaust gases follow an substantially upward path with respect to said engine orientation.

5. The intake and exhaust system for an internal combustion engine as claimed in claim 4, wherein the internal combustion engine is preferably horizontal in orientation.

6. The intake and exhaust system for an internal combustion engine as claimed in claim 4, wherein the internal combustion engine is preferably vertical in orientation

7. An exhaust system substantially as claimed in any of the preceding claims and illustrated with reference to the accompanying drawings.