BACKGROUND OF THE INVENTION The bicycle has been being developed since its invention, and today, it is intimately associated with the modern daily life as a transporting means, a sporting means and the like.

A connecting rod 21 of a conventional engine is run straight along the piston 12 movement direction passed through both the center of the crank pin inserting hole 15 in the larger end portion 22 and the center of the piston pin inserting hole 16 in the smaller end portion 23 at the

very moment that its piston 12 is positioned at the top dead center, as shown in Figures 1 and 2. At that time, therefore, the combustion pressure FCON prevailed in its cylinder 11 does not be converted to a force for rotating a crankshaft 13 because the centers of the piston pin, the crank pin and the crankshaft 13 are on a straight line. The larger diameter of the crank pin is, and in turn the larger end 22 of the connecting rod 21 is, the less an amount of work conducted by the piston 12 at the top dead center is.

Since a compression ratio at the top dead center is 11: 1 in an ideal state and 10: 1 in an actual state in a gasoline engine, and 24: 1 in an ideal state and 22: 1 in an actual state in a diesel engine, when the piston 12 is at the top dead center, a combustion pressure FCON obstructed by the straightened three centers is a major reason for knocking in the gasoline engine and low efficiency in the diesel engine.

The inventor of this invention proposed a connecting rod modulated in consideration of the aforementioned problems, which is disclosed in International Publication No. W089/07705. As shown in Fig. 3, although the modulated connecting rod in increasing an inertia force and an output force in comparison with a connecting rod of prior art, it also provides a transmission route through the three centers on a straight line, when the piston 12 is at the top dead center. The modulated connecting rod, therefore, does not secure increasing of the compression ratio. The prevailing combustion pressure FCON without the connecting rod 31 biased when the piston 12 is at the top dead center is obstructed to expand with very large force

and only straightly transmitted through the lowest point of the piston pin inserting hole 16 in the smaller end portion 33, the central point of the crank pin inserted into the crank pin inserting hole 15 in the larger end portion 32, and the center of the crankshaft 13. This is the most important reason for frustrating to try to increase a compression ratio.

SUMMARY OF THE INVENTION A biased crank pin according to the present invention provides the shortest straight length, through which the prevailing combustion pressure FCON is transmitted.

The prevailing combustion pressure FCON changes its course at the piston pin-inserting hole 16 in the smaller end portion 43 is toward a peripheral portion of the crank pin biased from its center. A clearance 44 is provided between the inner circumference of the crank pin inserting hole 16 of the connecting rod 41 and the circumference of the crank pin so that the clearance 44 is positioned over an upper portion of the circumference of the crank pin, at the very moment that its piston is positioned at the top dead center. The clearance 44 makes the combustion pressure FCON be converted to the crankshaft rotation force when the piston is not only at but also immediately before the top dead center, whereby the aforementioned problems regarding increasing the compression ratio is solved, and then a larger compression ratio, a more lightened and compact engine, and a more enhanced combustion efficiency is possible.

In accordance with the present invention, a biased connecting rod adapted to provide the shortest straight length for force transmission when a piston connected to the connecting rod is at the top dead center, wherein the connecting rod comprises: a smaller end portion; a larger end portion; a piston pin inserting hole in the smaller end portion moved rightward from the central axis of the connecting rod; a crank pin inserting hole in the larger end portion moved leftward from the central axis of the connecting rod so that an angle having a considerable sine value is provided between the connecting rod and a crank rod connected to it when the piston is at the top dead center; and a clearance formed on an upper portion of a crank pin inserted into the crank pin inserting hole.

The angle between the central line of the connecting rod and a line drawn from the center of the piston pin inserting hole and the center of the crank pin inserting hole is preferably set to provide the most sine value when a combustion pressure reaches the highest value.

It is also preferred that the clearance is limited to do not obstruct an oil membrane on a bearing of the crank pin at a high revolution speed.

BRIEF DESCRIPTION OF THE DRAWINGS Several preferred embodiments of the present invention will be explained with reference to the accompanying drawings, in which: Fig, 1 shows a prospective view of a crank system

comprising a conventional connecting rod; Fig. 2 shows a front view of the crank system shown in Fig. 1, wherein several parts are shown in a cross- section; Fig. 3 shows a front view of the crank system comprising another conventional connecting rod, wherein several parts are shown in a cross-section; and Fig. 4 shows a front view of the crank system comprising a connecting rod in accordance with a preferred embodiment of the present invention, wherein several parts are shown in a cross-section.

DETAILED DESCRIPTION OF THE INVENTION The above objects, other objects, features and advantages of the present invention will be better understood from the following description taken in conjunction with the attached drawings.

Now, preferred embodiments of the present invention will be described in detail with reference to the drawings.

As shown in Figures 1 and 2, in a conventional connecting rod 21, the prevailing combustion pressure FCON when the piston 12 is at the top dead center is transmitted to the crank pin and in turn to the center of the crankshaft 13 through the shortest straight length, that is, from the lowest point of the piston pin inserting hole 16 in the smaller end portion 23 of the connecting rod 21 to the crank pin inserting hole 15 in the larger end portion 22. Thus, at a compression ratio more than a usual compression ratio,

that is, 10: 1 in a gasoline engine 10: 1 or 22: 1 in a diesel engine, knocking in the gasoline engine and a low efficiency in the diesel engine is inevitable.

Fig. 4 shows a preferred embodiment of the biased connecting rod 41 so that a crankshaft rotation force is output even though the piston is at the top dead center according to the present invention. The connecting rod 41 has the shortest straight length for force transmission established through the center of the piston pin-inserting hole 16 in the smaller end portion 43 and the biased point on the circumference of the crank pin inserting hole 15 in the larger end portion 42 rather than the center of the crank pin inserting hole 15. Moreover, the connecting rod 41 has the clearance 44 on an upper portion of the circumference of the crank pin inserted into the crank pin inserting hole 15 in the larger end portion 42. Thus, there is provided an angle between the center of the connecting rod 41 and the center of the crank rod 14, which has a considerable sine value pursuant the trigonometry, even though the piston 12 is at the top dead center.

The piston pin-inserting hole 16 in the smaller end portion 43 of the connecting rod 41 is the point at which the prevailing combustion pressure FCON changes its direction. The more the piston pin inserting hole 16 in the smaller end portion 43 is biased from the piston movement direction, the more the prevailing combustion pressure FCON changes its direction so that the crankshaft rotation force is more output. If excessively biased, however, a pushing force in the rotational direction is strengthened, and then,

the crank rod 14 is forced out of the circumference, whereby the engine may be dithered and vibrated at a low revolution speed of less than 400rpm. Therefore, there is required that the crank pin inserting hole 15 in the larger end portion 42 is constructed to make the crank rod 14 be forced into the circumference so as to eliminate engine dithering and vibrating. Moreover, a bearing may be inserted into the clearance 44 between the inner circumference of the crank pin inserting hole 16 of the connecting rod 41 and the circumference of the crank pin so that an oil membrane is formed even on a high revolution speed, and in turn that the prevailing combustion pressure FCON is securely passed through the biased portion on the crank pin. The crank pin inserting hole 15 in the larger end portion 42 of the biased connecting rod 41 according to this embodiment is biased from a line through the piston pin inserting hole 16 in the smaller end portion 43 in the piston movement direction so that the piston pin inserting hole 16 is positioned in the right-upper portion of the connecting rod 41 while the crank pin inserting hole 15 is positioned in the left-lower portion in the attitude that the piston 12 is at the top dead center. A desirable degree of bias of the crank pin inserting hole 15 is affected by the diameter of the cylinder 11, shape of a jointing cap of the larger end portion 42, and the degree of bias of the crankshaft 13.

The clearance 44 should be limited so as to do not exert any over load on a bearing of the crank pin at a high revolution speed.

A test was tried as the piston pin-inserting hole 16 is moved rightward while the crank pin inserting hole 15 is moved leftward in the state that the central axis of the connecting rod is in alignment with the piston movement direction. In this test, the more the piston pin inserting hole 16 is moved, the larger the sine value of the biased angle when the piston 12 is at the top dead center, whereby the output force is increased. When the degree of movement of the piston pin-inserting hole 16 was over a proper value, engine dithering and vibrating at a low revolution speed was increased. This means that the degree of movement of the piston pin-inserting hole 16 should be modulated based on the lowest engine revolution speed, that is, an idle speed, and the degree of bias of the crankshaft 13. In other words, the more the piston pin-inserting hole 16 is moved rightward within a proper range, the more the output force is obtained.

The more the crank pin inserting hole 15 is moved leftward, the less the engine is dithered and vibrated. If the bias is excessively increased without the degree of bias of the crankshaft 13 considered and without a clearance 44 shaped, an over load may be exerted on the bearing of the crank pin.

In comparison with a conventional crank system, in a crank system in accordance with the present invention, ridges on the inner wall of the cylinder due to abrasion is decreased since the piston 12 is moved as the connecting rod 41 changes its direction from left to right when the piston 12 is at the bottom dead center, at which the prevailing combustion pressure FCON DK is lowest. In other words, biasing the piston pin inserting hole 16 rightward and the

crank pin inserting hole 15 leftward is one of important ways for preventing the gasoline engine from knocking, and enhancing a mechanical efficiency of the diesel engine. In this way, a more combustion efficiency was realized.

As above explained, by the construction of the biased connecting rod 41 according to the present invention, the combustion pressure FCON not only very at but also immediately before the time that the piston 12 reaches the top dead center is converted to the output force.

Accordingly, an instant acceleration is increased. Moreover, a compression ratio more than the ideal compression ratio of prior art is realized, and in turn the combustion efficiency is enhanced and a lightened flywheel is usable.

For example, when the highest combustion pressure FCON was 60 Kgf/cm, a test of output force in angle between the connecting rod 41 and the crank rod 14 shows the results, as follows.

Since such an angle of prior art was 180°, the output force when the piston 12 is at the top dead center is calculated as 60 Kgf/cm X sin 180 = 0 Kgf/cm.

Since such an angle in the present invention is not 180°, for example 165°, the output force when the piston 12 is at the top dead center is calculated as 60 Kgf/cm X sin 165 = 15.5 Kgf/cm.

Although from the piston at the top dead center, any output force is not obtained using the crank system of prior art, a considerable output force is obtained using the crank system in accordance with the present invention even from the piston at the top dead center. The more the

compression ratio is increased, the more the output force is obtained.

A driving test is tried using a 800cc-engine- equipped car, TICO, which is available form a car maker, DAEWOO AUTOMOBILE, in Seoul, Korea, while the connecting rod 21 of prior art and the connecting rod 41 according to the present invention are alternatively equipped, and then the results illustrated in Table 1.

Table 1: RESULTS OF A DRIVING TEST CONNECTINGRODOFINVENTIVE PRIORART CONNECTINGROD ManualGearStep1PossibletostartPossibletostart ManualGearStep2PoordrivingPossibletostart performanceatless than25Km/h ManualGearStep3PoordrivingGooddriving performanceatlessperformanceatmore than35Km/h thanat15Km/h ManualGearStep4PoordrivingGooddriving performanceatlessperformanceatmore than55Km/h thanat30Km/h ManualGearStep5PoordrivingGooddriving performanceatlessperformanceatmore than65Km/h thanat40Km/h Although technical spirits of the present invention has been disclosed with reference to the appended drawings and the preferred embodiments of the present invention corresponding to the drawings has been described, descriptions in the present specification are only for illustrative purpose, not for limiting the present invention.

Also, those who are skilled in the art will appreciate that various modifications, additions and substitutions are possible without departing from the scope

and spirit of the present invention. Therefore, it should be understood that the present invention is limited only to the accompanying claims and the equivalents thereof, and includes the aforementioned modifications, additions and substitutions.