A known connecting rod or"con-rod"includes two annular bearing shells, one of which is inserted in the bore or eye in the little end and the other of which is inserted in the bore or eye of the big end. The big end is split and the cap is secured by bolts which apply a crushing strain to the bearing.

According to the invention, there is provided a con-rod, including an integral bearing at one or both of the big end and little end.

According to another aspect of the invention, there is provided a connecting rod for an internal combustion engine, one or both of the big end and little end of the con-rod defining a bore to the inner surface of which a bearing material has been applied, for example, by physical vapour deposition, chemical vapour deposition or electroplating.

The lack of a bearing shell means that the bore or eye can be smaller resulting in weight saving on the rod and crank and therefore lower stresses. The engine may also be made narrower.

As there is no bearing, there is no bearing crush, and thus smaller bolts and bolt bosses can be used. About 25% of the bolt load in a conventional con-rod overcomes bearing crush.

This again reduces weight and the engine can be made narrower.

The shell in the conventional con-rod is arranged on a chamfer to each edge of the bore or eye. This can be reduced or eliminated by means of the invention which means that the con-rod can be made narrower and the crank pin length reduced resulting in weight saving on the con-rod and the possibility of making the engine shorter.

A con-rod according to the invention also has a higher load capability per unit mass. This means that the big end can be made narrower as can the small end, the crank pin length can be reduced, and the piston boss length can be increased. This provides weight saving on the con-rod and the possibility of the engine being shortened. This may also avoid the need for keystone rods.

By means of the invention a weight saving of 10-20% can be made in the big end mass of the con rod. The removal of the bearing shells accounts for 3-6% of the saving. The reduced bolt size accounts for up to 5% of the saving. The reduction in width results in a 5-10% saving and indeed possibly as much as 15%.

The bearing material can be any suitable material but may be aluminium tin, tin aluminium, copper, molybdenum disulphide, chromium nitride, lead bronze or suitable material on its own or in combination.

An embodiment of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Fig 1 is an elevation of a con-rod, the left side of which represents a prior known con rod and the right side of which represents the embodiment of the invention.

The prior known con-rod 10 shown in the left of the figure is a con rod for a passenger car with a diesel engine. The con rod 10 includes a little end 12 and a big end 14. The bore or eye 16 in the little end 12 includes a chamfer 18 circumferentially to each axial side of the bore or eye 16 and a steel backed bearing shell 20 is provided lining the bore 16 located by the chamfers 18.

The big end 14 includes a bore or eye 22 and similarly to the little end, includes chamfers 24 to the bore or eye 22 and a bearing shell 26 in the bore or eye 22. The big end 14 is in two parts secured together by bolts 28.

The right hand side of the con-rod 10 shown in the figure illustrates the embodiment of the invention. The same reference numerals will be used for the same or equivalent features.

Only the differences from the con-rod of the left hand side of the figure will be described.

In the con-rod 10 of the embodiment, the bearing shells 26 and 20 are not present, and the chamfers 18,24 also are not present. The inner surfaces 30,32 of the bore or eye 16 and bore or eye 22 are thus cylindrical. The inner surfaces 30,32 have been treated by physical vapour deposition to deposit a layer of AlSn. This layer 30 provides a bearing surface for the bore or eye.

In place of the technique of physical vapour deposition, other deposition techniques could be used such as chemical vapour deposition or electroplating, for example.

It can be seen that the centres of the eyes 16,22 are in the same place in the two con rods 10 shown. However, the con rod 10 of the embodiment is shorter. Thus the thickness of the material around the outer end of each eye 16,22 is reduced as clearly seen at X and Y in the figure. This is the direct result of removal of the shells 20,26. The diameter of the bore 22 in the big end of the conventional con rod 10 is 51.34mm and that diameter is reduced by the shells 20,26. In the con rod 10 of the embodiment the diameter of the bore 22 in the big end is 47.68mm Also the size of the bolts 28 used is reduced in the con rod 10 of the embodiment. This is because there are no bearing crush loads to overcome. The bolts 28 in the conventional con rod 10 are M8 bolts and the bolts 28 in the con rod 10 of the embodiment are M6 bolts. The thickness of the con rod 10 is also reduced, that is the dimension axially of the bores 16,22. In the known con rod 10 the thickness at the big end is 25.35 mm, while in the con rod 10 of the embodiment, the thickness at the big end is 23.65mm. The combined effect of these reductions in size and the loss of the bearing shells is a significant reduction in weight. The known con rod 10 weighs 532g while the con rod of the embodiment weighs 476g, a weight saving of 12%.