Connecting Rod for Internal Combustion Engine

Field of the invention

The present invention relates to a "Connecting rod for internal combustion engine" and more particularly to a connecting rod formed with an extension of stem and web in the elongate direction of big end profile.

Description of the prior art

An internal combustion engine includes a piston and a crankshaft connected to each other by a connecting rod, and the explosive force of an air-fuel mixture during the combustion stroke is transmitted to the crankshaft via the piston and the connecting rod.

In known type of connecting rods, they generally includes a small end on the piston side, a big end on the crankshaft side, and a stem portion connecting between the small end and the big end.

A piston pinhole is formed in the small end of the connecting rod through which a piston pin for connecting the piston is inserted. Similarly, at the big end, a crankshaft bearing hole is formed in which a crankpin of the crankshaft is positioned. The big end includes a big end main body and a bearing metal is fitted onto the inner surface of the big end main body.

Further the present design has a web and stem connecting the big end of the connecting rod together, and thereby .forming a stem portion for the connecting rod. This connecting rod big end stem profile results in high level of big end contact stress, which leads to increased bending stress for the connecting rod of the internal combustion engine.

The connecting rod is a member for transmitting the explosive force of the air-fuel mixture mentioned above, and hence it is necessary to ensure that the connecting rod has sufficient rigidity and strength, and it is free from stress impacts, and providing required level of lubrication.

Hence it is the main objective of the present invention to reduce the big end contact stress and provide a connecting rod with improved stress characteristics.

Another objective of the invention is to provide a connecting rod for an internal combustion engine with sufficient amount of lubrication. Yet another objective of the present invention is to provide a connecting rod with widened stem and big end joining area to suppress stress concentration.

Brief description of the present invention

The connecting rod for the internal combustion engine includes a small end connected to a piston, a big end connected to a crankpin, and a stem portion extending between the small end and the big end. In the connecting rod, a big end member that forms the big end and a stem member that forms the stem portion.

According to the present invention, the connecting rod big end stem profile is modified substantially. The profile of the stem and the web is widened significantly in a lateral axis at the. stem and big end joining area, such that the tangential radius formed between the big end and the stem is substantially increased. Thereby the big end contact stress is reduced and the degree of stress concentration at the portion between the stem member and the big end member can be reduced.

The connecting rod big end stem profile is provided such that the big end portion is having a passage in fluid communication with an axial bore for sufficient lubrication in the connecting rod. Also the lubricating passage extends axially to provide fluid communication between the crankshaft and the piston end portions.

The present invention makes it possible to distribute the load from centre point of big end, and make more load transfer area at the big end and stem joining area, thus reducing the degree of stress concentration at the big end portion of the connecting rod.

The load transfer from the piston to the crankshaft is distributed from the big end centre point to its periphery, and hence enough material can be removed at the centre part of the big end portion of the connecting rod in consideration to stress characteristics.

This arrangement allows to create low pressure while lubrication at the big end portion of the connecting rod, and enables to accumulate more amount of lubricating oil, thereby allowing more amount of lubricating oil to flow through the oil passage, and significantly improving the lubrication of the connecting rod, crank shaft and piston parts.

Brief description of the drawings

Figure 1 illustrates a representative view of a' scooter type motorcycle according to the present invention.

Figure 2 illustrates the cross sectional view of the engine assembly having embodiments according to the present invention.

Figure 3 illustrates the isometric view of the connecting rod according to the prior .art.

Figure 4 illustrates the isometric view of the connecting rod according to the present invention

Figure 5 illustrates the front view of the connecting rod according to the present invention

Detailed description of the invention

A selected illustrative embodiment of the present invention will be now described with respect to the accompanying figures.

Figure 1 is a side plan view of a scooter type motorcycle provided with an engine 102. This engine is provided with an improved lubrication structure according to an embodiment of the present invention. Any known scooter type motorcycle, as illustrated in Figure 1, can be divided into three major portions, the front portion, the middle portion and the rear/tail portion.

The front portion comprises of the head tube, the handle bar 105, the front suspension 103, the front wheel with necessary brakes and the body panels 109; the middle portion comprises of the floor board, the seat support 106, the fuel tank, the battery, the utility box etc; and the rear/tail portion comprises of the engine support, the riders seat 106, the rear shock absorber 104, rear fender and the back wheel with suspensions. assembling such a vehicle, especially the body covers 109, there are many sub assemblies and these are independently mounted onto the frame 101 at different locations. The body covers 109 are. mounted to the frame 101 using brackets.

Scooter-type vehicles, or scooters, include a frame assembly 101, which usually supports the body of a scooter, along with front and rear wheels. A frame assembly for a scooter-type vehicle comprises of at least one front wheel, at least one rear wheel and a vehicle body.

Typically, a frame structure 101 for a scooter type motorcycle comprises a main frame and may also have a sub-frame. The sub-frame is attached to the main frame using appropriate fastening members. All the other components such as the body panels 109, the engine 102, the electrical units are mounted on the main frame and the sub frame either directly or by means of brackets and fastening members..

The frame assembly includes a head tube, which supports a front wheel suspension assembly 103 of the vehicle. An upper frame extends from the head tube to a rearward end of the vehicle body. A swing arm 104 is pivotally supported by the upper frame and supports a rear wheel of the vehicle. The frame assembly may include a lower frame removeably coupled to the upper frame and defining a space 107 there between.

The sub-frame preferably supports at least one component of the scooter-type vehicle in the space, such as a fuel tank, for example. Typically, front 103 and rear 104 suspension assemblies are operatively positioned between the front and rear wheels and the frame assembly. The front suspension assembly 103 commonly is a telescopic fork arrangement, while .the rear suspension assembly 104 is a swing type arrangement. In a scooter, the rear suspension swing arm typically supports a power unit 102, which is configured to drive the rear wheel of the scooter.

The power unit 102, is coupled along with a transmission assembly 108, such as a drive shaft, drive belt, or chain and sprocket assembly. The frame assembly 101 of a scooter-type vehicle is an elongated structure, which typically extends from a forward end to a rearward end of the scooter. A scooter frame assembly generally is convex in shape, as viewed from a side elevational view. A handlebar assembly 105 and a seat assembly 106 are supported at opposing ends of the frame assembly and a generally open area is defined there between.

In Figure 2, the principal portion of the engine of the present invention is shown in cross-sectional view. As shown in this figure, the engine includes a crankcase 201, a cylinder block 202 connected to the crankcase 201, a cylinder head 203 to be connected to the cylinder block 202 and a cylinder head cover. These are clamped and fixed together via stud bolts and the like, thereby constituting the main structure of the engine 102. The crankcase has a structure in which the half cases 204 & 205 are integrally connected to each other. The halves cases and are formed by dividing the crankcase into right 205 and left portions 204. In the crankcase, formed of the combined half cases and, a crankshaft is rotatable bearing 206 supported. A connecting rod 207 is rotatable attached to a crankpin of the crankshaft 208 via a bearing located at the large-end thereof. A piston 209 is pivotally attached to the small-end of the connecting rod 207 via a piston pin. In this embodiment, there is provided one piston 209 and the engine 102 of the present invention is a single cylinder 4-cycle engine 102. The engine 102 of this embodiment generally includes the structure described above. However, the engine 102 further includes an inventive connecting rod 207. Figure 3 illustrates the connecting rod 207 as applicable in the prior art wherein the stem profile 303A having an I section is almost linear and perpendicular throughout is entire length thus leading to high contact stress. Hereinafter, the proposed connecting rod structure will be described with respect to Figure 4 and Figure 5.

The present invention is applied to a connecting rod 207 for an automobile reciprocating engine 102. The connecting rod 207 includes a small end on the piston side 302, a big end 301 on the crankshaft 208 side, and a stem portion connecting between the small end 302 and the big end 301. The small end 302 has formed with a piston pinhole 309 through which a piston pin for connecting a piston 209 is inserted; the big end 301 has formed therein a crankshaft-bearing hole (not shown in figure) in which a crankpin of the crankshaft 208 is positioned. The big end 301 has a structure including a big-end main body and bearing metals are fitted onto the inner surfaces of the big-end main body.

The present inventions attempts the connecting rod 207 with a new design such that the stem profile 303 and the web is widened significantly in an lateral axis at the stem 303 and big end joining area, thereby the big end 301 contact stress is reduced and the bending cum stress characteristics are improved.

According to the present invention, the connecting rod big end 301-stem profile 303 is changed. The connecting rod 207 incorporates a stem having an I section inner profile that extends from small end 302 to big end 301.' The stem 303 and the web is widened significantly in an lateral axis at the stem 303 and big end 301 joining area, such edge of the said stem profile merges with the big end 301 tangentially to its periphery 312 and thereby the big end 301 contact stress is reduced and the degree of stress concentration at the portion between the stem member and the big end member can be reduced. In other words, the gap between the outer edge of the profile 310 and the outer edge of the stem 311 is maintained constant till the linear portion A-A1. The connecting rod big end stem profile 303 is provided such that the big end portion 301 is having a passage 306 in fluid communication with an axial bore 306 for sufficient lubrication in the connecting rod 207. Also the lubricating passage 306 extends axially to provide fluid communication between the crankshaft 208 (Not shown in figure) and the piston end 301, 302 portions. Figure 5 illustrates the front view of the connecting rod 207 incorporating the present invention. Here A-A1 is the linear portion as shown in the figure. In this portion the edge of the said I section profile is straight. After said section A-A1, the inner profile edge takes a curved path such that it is tangential to the periphery 312 of the big end.

The present invention makes it possible to distribute the load from centre point of big end 301, and makes more load transfer area at the big end 301 and stem joining area, thus reducing the degree of stress concentration at the big end 301 portion of the connecting rod 207.

The load transfer from the piston 209 (Not shown in figure) to the crankshaft 208 (Not shown in figure) is distributed from the big end 301-centre point to its periphery, and hence enough material can be removed at the centre part of . the big end 301 portion of the connecting rod 207 inconsideration to stress characteristics.

This arrangement allows to create low pressure while lubrication at the big end 301 portion of the connecting rod 207, and enables to accumulate more amount of lubricating oil, thereby allowing more amount of lubricating oil to flow through the oil passage 306, and significantly improving the lubrication of the connecting rod 207, crank shaft 208 and piston parts 209.

The improved lubrication of the connecting rod 207, crankshaft 208 and piston parts 209 allows for suppressing the noise generated during the operation of the internal combustion engine 102.

The present invention allows increasing the load transfer area at the stem 303 and big end 301 joining area, thus eliminating the need to increase the thickness to achieve stress dispersion.

Therefore, sufficient strength and rigidity can be secured without increasing the weight of the connecting rod, thereby making it possible to sufficiently satisfy performance requirements placed on the connecting rod, such as high strength, high rigidity, and light weight.

Part numbers associated with the drawings

101. Frame 204. &
205. Half cases of the
102. Engine crankcase
103. Front suspension assembly
206. Bearing support
104. Rear shock absorber
207. Connecting rod assembly
208. Crankshaft
105. Handle bar
209. Piston
106. Seat assembly
301. Big end of the piston rod
108. Transmission assembly
302. Small end of the piston rod
109.' Body panel
303. Stem profile
201. Crankcase
303A. Stem profile in prior art
202. Cylinder block
306.Passage for fluid
203. Cylinder head communication
309. Piston pinhole
310. Outer edge of the altered stem
311. Outer edge of the stem profile
312. Outer periphery of the big end

Claims We claim:

1. A connecting rod of a crankshaft assembly for an internal combustion engine having a big end and a small end connected by a stem having an I section profile that extends from the small end to the big end characterised in that the edge of the said stem profile merges with the big end tangentially to its periphery.

2. The connecting rod of a crankshaft assembly as claimed in claim 1 wherein the distance between the outer edge of the said stem and the said edge of the stem profile remains constant till the said stem profile edge is linear.

3. The connecting rod for internal combustion engine substantially described and illustrated with reference to the accompanying drawings.