FIELD OF INVENTION

The present invention relates to an internal combustion engine and more particularly, to the construction of the cylinder head for an internal combustion engine so as to achieve lightweight engines without compromising with the stiffness and heat dissipation.

BACKGROUND OF THE INVENTION

Internal combustion engines are used as prime movers in many vehicles. These engines produce significant amounts of heat during the course of their operation. A part of the heat energy generated inside the combustion chamber is dissipated to the atmosphere.
The dissipation of heat from the engine at higher rate is desirable to keep the engine temperature within the desirable limit. To achieve proper cooling, engines are fitted with various cooling systems. These cooling systems rely on a flow of fluid over or through the engine casing or engine components as a means of transferring heat from the engine to the environment. Inefficient engine performance and failure of engine components have been observed due to failure of heat transfer from the engine.

Air is generally used as an agent for transferring heat from the engine to the ambient and such engines are often referred to as being "air-cooled" engines. A typical air-cooled engine consists of at least one cylinder structure encasing at least one reciprocating piston and a cylinder head. The cylinder head is mounted atop the cylinder block and provides a combustion chamber as well as for housing intake and exhaust valve or port mechanism depending upon the engine type.

Irrespective of the engine types and irrespective of how many cylinders or how each cylinder is physically oriented with respect to another cylinder, the engine is usually positioned to permit a flow of air over and about the engine. To enhance the rate of heat transfer to the ambient air generated by the combustion of fuel and air within the engine, or more precisely the heat generated within the cylinder block and the cylinder head where such combustion takes place, the engine is often fitted with a number of cooling fins which extends outwardly from the from the engine. It is widely recognized within the art of constructing engines which employ cooling fins, that cooling fins serve to increase the effective surface areas from which heat is transferred to the environment generated from within the engine and its associated components. With increase in effective surface area provided by the cooling fins, the rate of radiative and convective heat transfer to the environment is increased. Number, size, orientation, design and position of fins on the engine further influence cooling capacity of such fins. However, the number, size and design of fins have considerable bearing on the weight of engine and in an attempt to produce lightweight engines, a trade off between thermal and structural stability becomes difficult to obtain. In a low weight engines, stiffness of the structure reduces which in turn can increase the warpage or distortion related problems owing to the mechanical stresses due to pre-tensioning and gas forces apart from thermal loads due to the combustion. The pre-tensioning forces of the cylinder head originate from the screw connection with the cylinder block, while gas forces are caused by the combustion in the combustion chamber. For an instance, the pre-tensioning force applied to the cylinder head may results in the distortion of the camshaft hole and even failure of valve mechanism whereas, increased structural stiffness may avoid these problems, but may result in failure due to inefficient heat transfer.

SUMMARY

Accordingly, the present invention provides a cylinder head for an internal combustion engine that provides sufficient heat dissipation without compromising with the structural stiffness and stability and at the same time the weight of the engine is kept substantially low. In the present invention fins are provided on the studs at suitable locations in a direction such that they add to the overall stiffness of the stud.

In a preferred embodiment of the invention, the fins are provided on the studs that are near to the combustion chamber and spark plug. Due to proximity of the studs to combustion chamber and spark plug, the heat transfer through the fins provided on the said studs sufficiently Increases. Thus, even for engine with reduced mass the fins provided on studs aids in increasing structural stability without compromising with the heat transfer. Other advantages and features of the invention will become apparent from the following description including the drawings and claims.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 depicts a two-wheeled vehicle embodying the present invention.

Figure 2 depicts a cylinder head of a four-cycle internal combustion engine.

Figure 3 depicts the studs provided in cylinder head embodying the fins as per the invention.

Figure 4 depicts the cylinder head of a four-cycle internal combustion engine embodying the present invention.

DETAILED DESCRIPTION OF THE INVENTION

With reference to figures a motorcycle 01 having a four-stroke, air-cooled internal combustion engine 02 is illustrated the engine 02 comprises a cylinder head 03 positioned over one end of a cylinder formed in a cylinder block. A piston (not shown in figure) is reciprocably mounted within cylinder of the cylinder block to define a hemispherical combustion chamber 04. The entire combustion chamber 04 is formed by the clearance volume between the upper surface of the piston and the lower surface of the cylinder head 03. The cylinder head also accommodates input 05 and exhaust valves 06, camshaft mechanism 07 and the spark plug. Plurality of studs 08 are provided in the cylinder head 03 to bolt the cylinder head with the cylinder block.

Referring to figure 2, figure 3 and figure 4, a plurality of fins 09 are provided on the external surface of the studs 08. The said fins 09 are provided such that the fins 09 increases the stiffness of the studs 08 and as a result the overall stiffness of the cylinder head 03 also increases against the pre-tensioning forces 11, further the fins 09 owing to there orientation guides the cooling air so as to achieve effective cooling.

In a preferred embodiment the studs 08 that are in close proximity of the combustion chamber 04 are provided with higher density of fins as large amount of heat can be dissipated through these. Thus, providing effective cooling without compromise with stiffness and increasing mass of the cylinder head 03.

Table 1 shows the difference in temperature in cylinder cover, cylinder head and cylinder block with and without fins on the studs as can be appreciated that a considerable difference in temperature can be obtained. These data are for a typical four-stroke small displacement engine and temperature drop would vary from design to design and engine capacity.

Table 2 shows the reduction in distortion of the camshaft hole and the studs as an example when the studs are provided with fins compared to the studs without fins. Thus, the stiffness also increases without much increase in the mass of the assembly.
It should also be noted that the configuration according to the above-mentioned embodiment is an example of the present invention. The invention can also be employed in other kinds of engines, and various modifications may be made therein without departing from the spirit of the present invention.

WE CLAIM

1. A cylinder head for an internal combustion engine having peripheral boundaries comprising;

a recess having an upper substantially planar peripheral boundary and side peripheral boundaries for cooperating with a piston and cylinder in a cylinder block to define a combustion chamber,

at least an intake port integrally formed with the cylinder head configured to receive charge having an interior wall, that defines intake passageway to the combustion chamber, an intake valve, disposed in the intake port and having head and stem portions reciprocable on an axis for controlling communication of the inlet port with the combustion chamber,

at least an exhaust port integrally formed with the cylinder head configured to discharge exhaust gases, having an interior wall, that defines exhaust passageway from the combustion chamber, an exhaust valve, disposed in the exhaust port and having head and stem portions reciprocable on an axis for controlling communication of the exhaust port with the combustion chamber, and

a camshaft assembly for actuating the said intake and the said exhaust valves,
a plurality of studs formed in the cylinder head for bolting the said cylinder head to the cylinder block wherein, the outer surface of the said hollow studs have a plurality of fins disposed such as to increase the stiffness against structural deformation and heat transfer.

2. A cylinder head for an internal combustion engine as claimed in claim 1, wherein the said stud is preferably a hollow stud.

3. A cylinder head for an internal combustion engine as described and shown in the specification.