0535

CYLINDER HEAD ASSEMBLY

FIELD OF INVENTION

The subject matter described herein, in general, relates to an internal combustion engine, and in particular relates to a cylinder head assembly of the internal combustion engine.

BACKGROUND

Cylinder head assembly design of an internal combustion engine plays an important role in deciding fuel economy, quality of exhaust emissions, and torque output of the internal combustion engine. Making an engine more efficient or more economical is an exercise in compromise as different competing variables affect the performance of the engine.

Conventionally, various designs are employed for deriving the desired fuel economy and low emission levels. One such design involves use of a stratified or layered charge engine. Here, ignition begins in a layer, which is made up of pockets of a rich mixture surrounded by a leaner mixture. A leaner average air-fuel ratio provides greater fuel economy and less exhaust emissions. To obtain the desired air-fuel ratio, fuel injectors are used. Since use of injectors require deployment of sensors, ECU, and the like, such a design leads to complex manufacturing, servicing difficulties, and an increased cost. Therefore, injectors are particularly employed for multi-track multi-cylinder engines where the complexity and high input cost is offset by commensurate gains. However, injection systems for single track vehicles, particularly for small volume motorcycles, do not offer incentives in terms of fuel economy as compared to the extra

cost and complexities involved. Moreover, use of injectors requires more control and energy, which has an adverse impact on the size, weight, and cost of the internal combustion engine.

An alternate design for spark ignition engines includes the use of two spark plugs in a single combustion chamber. By using two spark plugs, the time required for combustion in the combustion chamber is shortened. However, fuel consumption is more and exhaust emissions are high. Further, while using a leaner air-fuel ratio, the torque output produced is low.

There is, therefore, a need of a cylinder head assembly, which overcomes above said problems, thereby providing a more economical and a more efficient internal combustion engine. SUMMARY

The subject matter described herein is directed to a cylinder head assembly of an internal combustion engine. The cylinder head assembly includes a cylinder head, a combustion chamber, a fuel supply device for supplying fuel to the combustion chamber, and an intake pipe that connects the fuel supply device to the cylinder head. The cylinder head has a plurality of intake ports for receiving the fuel from the fuel supply device and delivering the fuel to the combustion chamber. For example, in an embodiment, there may be two intake ports, i.e. a first intake port and a second intake port. The intake pipe, which includes a plurality of intake passages such as a first intake passage and a second intake passage, connects the fuel supply device with the intake ports. The intake passages are aligned with the

corresponding intake ports for supplying the fuel from the fuel supply device to the intake ports.

In one embodiment, on acceleration, the fuel supply device supplies air fuel mixture first through the first intake port and when the first intake port is substantially open, then through the second intake port. The opening of the second intake port is done mechanically after a particular percentage of total pull of a throttle cable is reached. Therefore, under full throttle conditions both the ports are fully uncovered. Similarly, on deceleration, if the power requirement decreases beyond the particular percentage of total pull of the throttle cable, the second intake port is closed. The cylinder head assembly of the present subject matter is configured to provide the regular functionalities of an internal combustion engine while achieving enhanced fuel economy. Further, the engine is designed to give higher output power with lower exhaust emissions as compared to the existing engines.

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 is it intended to be used to limit the scope of the claimed subject matter.

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:

Fig.l provides a cross sectional view of a cylinder head assembly of an internal combustion engine with respect to one embodiment of the present invention.

Fig.2a, 2b & 2c illustrate a perspective front view, side view and cross section view respectively, of an intake pipe of the cylinder head assembly of Fig.l. Fig.3 illustrates a sectional view of a cylinder head of the cylinder head assembly ofFig.l.

Fig.4 shows a perspective bottom view of the cylinder head of Fig.3.

Fig.5 illustrates a right side view of the cylinder head of Fig.3.

Fig.6 illustrates a perspective top view of the cylinder head of Fig.3. Fig.7 illustrates a perspective front view of the cylinder head of Fig.3.

Fig.8 illustrates a rear side view of the cylinder head of Fig.3.

Fig.9 illustrates a left side view of the cylinder head of Fig.3. DESCRIPTION

A cylinder head assembly for an internal combustion engine, according to one embodiment of the present subject matter, is described. The cylinder head assembly described herein includes a cylinder head, a combustion chamber, a fuel supply device, and an intake pipe connecting the fuel supply device to the cylinder head. The fuel supply device can be for example, a round piston type or a slide valve carburetor having a slide valve disposed therein. The cylinder head includes a plurality of intake ports. The intake pipe, having a plurality of intake passages, connects the fuel supply device with the intake ports. The intake passages align with the corresponding intake ports and supply the fuel from the fuel supply device to the intake ports.

The intake ports provide for injecting the fuel into the combustion chamber where the fuel undergoes combustion for driving the vehicle. In one embodiment, there may be two intake ports, i.e. a first intake port and a second intake port. The first intake port is also referred to as a charging port and the second intake port is also referred to as a volumetric port. The charging port is provided as a tangential port, i.e. the port is directed tangentially to a cylinder bore surface in order to produce swirling movement of the air fuel mixture in the cylinder. On the other hand, the volumetric port produces a charge stream directed approximately against the centre of the cylinder which helps in filling the cylinder with the air fuel mixture. The system is designed in such a way that the air fuel mixture enters the combustion chamber first through the charging port and then, when the charging port is substantially open, through the volumetric port also. Under low load conditions, a comparatively lean mixture enters the combustion chamber through the charging port leading to improved torque output, less fuel consumption, and low emissions. When requirement of torque is high and during high load conditions, a comparatively rich mixture enters through volumetric port while a relatively lean mixture enters through the charging port near the walls of the combustion chamber. Thus, torque output is high while at the same time fuel consumption and emission levels are low.

To control the supply of fuel, a throttle valve is disposed in the fuel supply device. During acceleration, the throttle valve mechanically opens the charging port. Once the charging port is fully opened, the throttle valve opens the volumetric port to supply extra air-fuel mixture to the combustion chamber that is required for higher acceleration. The change over from the charging port to the volumetric port is done after a particular

percentage of total pull of a throttle cable is reached. Due to this an optimum air-fuel mixture is achieved in the combustion chamber for different speeds of the vehicle thereby resulting in enhanced fuel efficiency.

As described above, the combustion of the fuel entering the charging port is nearly complete due to the additional charge motion produced by the special construction of the tangential port. Further, the fuel supply device can be provided with a full load power jet, which may be arranged in the direction of the volumetric port. The full load power jet can be used to provide additional power during quick acceleration and high speed operating conditions. As the present cylinder assembly provides for selection of intake ports, and thereby air-fuel ratios, based on the throttle position, the present cylinder head assembly achieves an enhanced fuel economy with lower fuel consumption at various load requirements. Further, the cylinder head assembly yields higher engine output with lower exhaust emissions. Moreover, the construction of the intake pipe is such that the transfer of vibration from the cylinder head to the fuel supply device is reduced.

Fig.l illustrates a cross sectional view of a cylinder head assembly 100 of an internal combustion engine according to one embodiment of the present subject matter. As shown in Fig.l, the cylinder head assembly 100 includes a cylinder head 105, an intake pipe 110, a combustion chamber (not shown in the figure) , and a fuel supply device 115. The fuel supply device 115 supplies air-fuel mixture to the cylinder head 105 via the intake pipe 110.

The fuel supply device 115 can be a slide valve carburetor or a round piston carburetor. In such a carburetor, a piston moves up and down in its chamber forming a

throttle device to control the air fuel mixture, or a throttle device can be additionally provided with a throttle valve.

Further, the intake pipe 110 includes two intake passages, 120a and 120b (collectively referred to as intake passages 120), and a wall 125 that separates the two intake passages 120a and 120b.

Fig.2a illustrates a perspective front view of the intake pipe 110 including the intake passages 120, and the wall 125. As described above, the intake pipe 110 is connected at one end to the fuel supply device 115, also referred to as carburetor 115, and at the other end to the cylinder head 105. The wall 125 separates the two passages 120 through out the length of the intake pipe 110. As a result, the intake passages 120a and 120b run substantially parallel to each other in the intake pipe 110.

Fig.2b illustrates a side view of the intake pipe 110 having an upper end 205 and a lower end 210. The upper end 205 is connected to the carburetor 115 and the lower end 210 is attached to the cylinder head 105. The lower end 210 of the intake pipe 110 is made up of a metal, such as aluminum, and is extended to the upper end 205 by moulding an elastomeric material over the metal. Such a construction of the intake pipe 110 facilitates the reduction of transfer of vibrations from the cylinder head 105 to the carburetor 115. Further, the lower end 210 is clamped to the right side of the cylinder head 105. Fig.2c illustrates a cross section view of the intake pipe 110 that supplies the fuel from the carburetor 115 to two intake ports 215a and 215b, collectively referred to as intake ports 215, which open inside the combustion chamber. The first intake port 215a is referred to as the charging port 215a and the second intake port 215b is referred to as the

volumetric port 215b. The intake passages 120a and 120b align with the intake ports 215a and 215b respectively inorder to supply the fuel from the carburetor 115 to the cylinder head 105. The carburetor 115 supplies the fuel first to the charging port 215a and thereafter to the volumetric port 215b. The volumetric port 215b begins to open only when the charging port 215a is opened substantially fully. The opening of the volumetric port 215b starts only after a particular percentage of the total pull of the throttle cable is reached.

Fig.3 shows a sectional view of the cylinder head 105 according to one embodiment of the present subject matter. The cylinder head 105 includes two intake valves 305a and 305b (collectively referred to as intake valves 305) , which control the flow of air-fuel mixture into the cylinder head 105. The opening and closing of the intake valves 305 are controlled by a camshaft disposed inside a cam chain chamber 310. The camshaft is connected to a crankshaft via an endless chain. When the crankshaft rotates, the rotational motion is transferred to the chain, which in turn drives the camshaft. The movement of the camshaft controls the opening and closing of the intake valves 305.

The intake valves 305 are disposed within valve guides 315a and 315b, collectively referred to as valve guides 315 hereinafter. The valve guides 315 are sealed by valve stem oil seals 320a and 320b collectively referred to as seals 320 hereinafter. The valve stem oil seals 320 keep excess lubricating oil out of the combustion chamber. The combustion chamber, where the fuel is burnt, is positioned on the bottom side of the cylinder head 105. The cylinder head 105 receives the air-fuel mixture from the carburetor 115 through the intake valves 305 and passes the air-fuel mixture to the combustion chamber.

In operation, during the upward movement of a piston in the combustion chamber, the air-fuel mixture present in the combustion chamber is compressed due to pressure exerted by the piston. Two spark plugs 325a and 325b (collectively referred to as spark plugs 325), are fitted in the cylinder head 105 in order to generate an electric spark to ignite the compressed fuel. The combustion of the fuel produces exhaust gases that travel from an exhaust valve to an exhaust manifold (not shown in the fig.).

Fig.4 illustrates a perspective bottom view of the cylinder head 105 with respect to one embodiment of the present subject matter. The bottom side of the cylinder head 105 is adapted to be mounted directly on to a cylinder block. The bottom side corresponds to a section of the combustion chamber in the cylinder head 105 having a pent roof shape. The section of the combustion chamber is a major arc of a circle at the boundary where the combustion chamber joins with the surface of the bottom side.

Fig.4 further illustrates the intake ports 215 which open inside the combustion chamber. In operation, during the suction stroke of the engine, the air-fuel mixture enters the combustion chamber through the intake ports 215. The carburetor 115 supplies the fuel via the intake passages 120a and 120b to the intake ports 215a and 215b respectively. The fuel is supplied first to the charging port 215a and thereafter to the volumetric port 215b. The change over to the volumetric port 215b is done mechanically after a particular percentage of the total pull of a throttle cable. The opening of the volumetric port 215b begins when the charging port 215a is opened fully. In another embodiment, the volumetric port 215b may be opened after the charging port 215a is substantially open. Therefore under full throttle conditions, both the ports are fully opened.

In another embodiment of the present subject matter, throttle valves to control the delivery of air fuel mixture to the intake ports 215 are provided inside the carburetor 115. As the vacuum between a throttle valve and the piston changes, the piston moves up and down in the combustion chamber. This causes an attached tapered needle to move in or out of a power jet of the carburetor 115 controlling the fuel. The power jet is a fuel metering device that comes into operation during the operation of the vehicle in a wide open throttle condition. The additional fuel is injected into the volumetric port 215b along with the air, to meet the requirements of additional power during quick acceleration and high speed operating conditions. Further, the throttle valves open successively in a register like manner, such that the charging port 215a is opened first followed by the opening of the volumetric port 215b. The throttle valve mechanically opens the charging port 215a during acceleration. Once the charging port 215a is fully opened, the throttle valve opens the volumetric port 215b in order to supply the extra air-fuel mixture to the combustion chamber that is required for higher acceleration. Similarly, on deceleration, when the power requirement decreases, the volumetric port 215b is closed slowly, and when it decreases to a value below the particular percentage of the total pull of a throttle cable, the volumetric port 215b is closed completely.

Each opening of the intake ports 215 further houses a seat for the intake valves 305. Diametrically opposite to the intake ports 215, an opening of an exhaust port 405 is disposed. During the exhaust stroke, the exhaust port 405 provides a path for the exhaust gases to exit from the combustion chamber to the exhaust manifold via the exhaust valve, which is also housed on a seat in the bottom side (not shown in the fig.).

On both sides of the exhaust port 405, the combustion chamber houses two openings 410a and 410b for the spark plugs 325a and 325b, respectively. On assembly, the tip-end of each of the spark plugs 325 is disposed substantially opposite to each other in the combustion chamber. In operation, the spark plugs 325 provide a spark nearly at the end of the compression stroke of the engine, which results in flame propagation and a subsequent power stroke. An opening for the cam chain chamber 310 is further disposed adjacent to the combustion chamber.

Fig.5 illustrates a perspective view of a right side of the cylinder head 105 when viewed in the direction y as shown in Fig.4. Both the volumetric port 215b and the charging port 215a are disposed side by side such that the volumetric port 215b is disposed above the charging port 215a. The volumetric port 215b runs substantially parallel to the charging port 215a up to the combustion chamber.

Further, the charging port 215a is strongly inclined towards a valve axis and is designed as a tangential or swirl port to incorporate only a low curvature. The tangential port is directed tangentially to the cylinder bore surface in order to produce necessary swirl motion of the intake charge about the cylinder bore axis. In the current twin port design, the entry of the charging port 215a is located relatively towards the bottom of the cylinder head 105, which is close to the combustion chamber.

The charging port 215a produces a flow that hits the cylinder wall of the combustion chamber tangentially. This leads to a formation of a strong swirling movement in the cylinder head 105. The charging port 215a defines an edge at the point where the charging port 215a joins with the combustion chamber to provide a swirl

action. Furthermore, three threaded holes 505 are provided on the right side of the cylinder head 105 for clamping the intake pipe 110.

On the other hand, the volumetric port 215b is designed to have a stronger curvature as compared with the charging port 215a, but shows a lower inclination towards the valve axis. The volumetric port 215b further produces a charge stream directed approximately against the centre of the cylinder head 105, which helps in filling of the combustion chamber with the air-fuel mixture.

During the normal operation of the vehicle, the air-fuel mixture is supplied by the tangential port. Therefore, when the vehicle is driven at normal speeds (~ less than 50 kni/hr) , only the tangential port is uncovered by the throttle to supply the necessary air- fuel mixture to the engine.

Under low load conditions, a comparatively lean mixture enters the combustion chamber through the charging port 215a. The provision of two spark plugs 325 results in initiation of sparks at two places in the combustion chamber. The combustion of the air- fuel mixture is nearly complete due to the additional charge motion produced by the special construction of the charging port 215a. This results in improved fuel economy of the engine as compared to the conventional engine. In addition, the combustion of lean fuel mixture received from the charging port 215a is completed in a comparatively shorter duration, leading to improved torque output, less fuel consumption, and low emissions.

However, during high load conditions, a comparatively rich mixture enters through the volumetric port 215b in the region of spark plugs 325 and a generally lean mixture enters through the charging port 215a near the walls of the combustion chamber.

Therefore, during the power stroke, even while the lean mixture is maintained in the combustion chamber, the torque output is high and at the same time fuel consumption and emission levels are relatively low.

Fig.6 illustrates a perspective top view of the cylinder head 105. According to one embodiment of the present subject matter, the top side of the cylinder head 105 is inclined at an acute angle to a plane defined by the bottom side of the cylinder head 105. This helps in easy access and assembling of different components. Further, the top side provides housing for the cam shaft assembly and a valve train. In addition, a cover can be fastened on the top side of the cylinder head 105 for safety and protection. As shown the two intake valves 305 are disposed within the valve guides 315, while the exhaust valve is disposed in a valve guide 605. On assembly, the configuration is such that the stem end of the intake valves 305 is disposed in the valve guide 315 on the top side of the cylinder head 105, while the face end of the intake valves 305 is disposed inside the combustion chamber towards the bottom side of the cylinder head 105.

Further, in Fig.6, a part section of the opening 410a, which houses the first spark plug 325a, is viewable. As illustrated, the opening 410a is disposed on a side wall of the cam chain chamber 310. On the other side of the cam chain chamber 310 an opening 610 is disposed to provide an access route to the first spark plug 325a from the cam chain chamber side.

Fig.7 illustrates a front view of the cylinder head 105 when viewed in the direction y as shown in Fig 4. An opening 410b is provided that extends to the combustion chamber and provides housing for the second spark plug 325b.

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PCT/IN2008/000535

Fig.8 illustrates a rear view of the cylinder head 105 when viewed in the direction y as shown in Fig 4. The rear view corresponds to a wall of the cam chain chamber 310, wherein the opening 610 is provided.

Fig.9 illustrates a perspective left side view of the cylinder head 105 when viewed in the direction y as shown in Fig 4. The exhaust port 405 is provided on the left side of the cylinder head 105, which extends to the combustion chamber on the bottom side of the cylinder head 105. During the exhaust stroke, the exhaust gases are removed from the combustion chamber through the exhaust port 405 into the exhaust manifold.

The test results, according to an embodiment of the present invention, conducted on a 125 cc engine are as follows:

It can be understood from table 1 above that the use of the new configuration reduces the emissions of toxic gases such as carbon monoxide (CO) , HC, and NOx. The emission of CO is reduced from 0.55 g/km to 0.29 g/km while the emission of HC is reduced from 0.5 g/km to 0.41 g/km. Further, the emission of NOx is reduced to 0.40 g/km from 0.44 g/km. The table further illustrates that the present engine provides greater power of 10.5 Ps with lower fuel consumption thereby achieving greater fuel efficiency.

The aforementioned versions of the subject matter and equivalent thereof have many advantages, including those, which are described below.

The cylinder head assembly yields higher engine output with lower exhaust emissions. Also, the cylinder head assembly achieves an enhanced fuel economy with lower fuel consumption under various load requirements. Moreover, the construction of the intake pipe results in reduced transfer of vibrations from the cylinder head to the fuel supply device. Further, due to the present design of the intake ports, the optimum air-fuel mixture is achieved in the combustion chamber thereby resulting in enhanced efficiency of fuel. Therefore, even while the lean mixture is maintained in the combustion chamber, the torque output is high and at the same time fuel consumption and emission levels are relatively low.

Although the subject matter has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternate embodiments of the subject matter, will become apparent to persons skilled in the art upon reference to the description of the subject matter. It is therefore contemplated that such modifications can be made without departing from the spirit or scope of the present subject matter as defined.