GB2130337A - Connecting rod for an internal combustion engine - Google Patents

Abstract

A connecting rod for an internal combustion engine comprises two substantially identical side parts (21,22). Each side part has a central web (23) and enlarged ends with journal sleeves (28, 29). The two side parts are joined together face-to-face solely by means of a pair of bearing bushes (31,32) which are an interference fit within respective aligned journal sleeves (28,29). <IMAGE>

Description

SPECIFICATION Connecting rod for an internal combustion engine This invention relates to connecting rods for internal combustion engines, especiallyforfractional horsepowertwo-cycle engines.

The manufacture of a conventional connecting rod is a comparatively expensive procedure. Generally it starts with a casting orforging and requires careful and expensive machining. It is an object of this invention to provide a connecting rod construction which can be formed from two relatively inexpensive stamping and two bearing bushes. The assembly is comparatively inexpensive, and is reliable and accurate.

Aconnecting rod according to this invention comprises a pair of, preferably substantially identical, side parts each having a central web, a pair ofjournal sleeves one adjacent the respective ends of each side part, and a pair of bearing bushes each including a central bearing bore having an axis and an outside surface. This surface is an interference fit in a respective journal sleeve of both ofthe side parts, the two side parts being in face-to-face contact with each otherwith the journal sleeves embracing and holding the two bearing bushes with their axes parallel, said side parts being joined together only by means ofthe bearing bushes and being secured to said bushes only by an interference fit therewith.

According to a preferred but optional feature of the invention the journal sleeves are internally tapered to provide a retentive force to the bearing bushes.

The above and other features ofthis invention should be fully understood from the following detailed description with reference to the accompanying drawings in which: Fig. lisa plan view of a prior art connecting rod; Fig. 2 isa side view ofthe connecting rod of Fig. 1; Fig. 3 is a cross-section at line 3-3 of Fig. 1; Fig. 4 is an exploded view partly in axial cutaway cross-section and partly in side elevation ofthe presently preferred embodiment of the invention; Fig. 5 is a plan view of the connecting rod of Fig. 4; Fig. 6 is a cross-section at line 6-6 of Fig. 4; and Fig. 7 is a cross-section at line 7-7 of Fig. 5.

Fig. 1 shows a connecting rod 10 according to the prior art. Such a rod customarily includes a pair of journal ends 11, which have respective bearing surfaces 13, 14. If preferred, these surfaces can act as meansto hold a friction bearing insertthereinwith bearing surfaces, or even a roller or ball bearing.

Whichever the arrangement, the faces 15, 16 of the rod must be accuratelyfinished, the centres ofthe journal ends must be accurately located, and the axes must be parallel. Because the material is a forging, the machine operations, even though conventional, are still expensive and time consuming. It is an object of this invention to provide a connecting rod with the advantages of the prior art, but which can be made inexpensively from stamping and inserts.

In Fig. 4there is shown an explodedviewofa connecting rod 20 according to the invention. This rod comprises a pair of side parts 21, 22 which are identical to one another. Therefore only the side part 21 will be described in detail. It includes a central web 23 which has a stiffener rib 24 stamped therein. This rib has a central arched portion 25 (Fig. 6).

At each end of the side partthere is an enlargement 26,27 and extending from each enlargement is a journal sleeve 28,29 respectively. These journal sleeves may readily be formed in the stamping operation simply by piercing and extruding the material oftheflat piece of metal from which the part is made. Preferably each of the journal sleeves has a slight taper shown by angle 30. This is a very gradual taper, but when present can serve a valuable purpose as described below. The taper angle will ordinarily be less than one degree conical included angle. If preferred, there need be no taper.

A pair of bearing bushes 31,32 is provided. Each has a respective inside bearing surface 33,34 and a respective outside surface 35,36. The bearing surfaces 33 and 34 could be the inside surfaces of an inner bearing race, instead of the bearing surface of a frictional bearing. These are fully equivalentfor purposes of this invention.

The bearing surfaces 33 and 34 have respective central axes 37,38. If desired, short lead-in chamfers 39,40,41,42 maybeformed atthe inward entrances of the journals sleeves to assist insertion ofthe bearing bushes. The outside diameter ofthe surfaces 35 and 36 is intended to be an interference fit with the inside ofthe respective journal sleeve. The outside surfaces 35 and 36 are preferably cylindrical. When the tapered construction is used, the outerdiameterwill be about the same as the nearest end ofthe respective journal sleeve, and somewhat oversized relative to the free end ofthe respective journal sleeve. When there is no taper,theouterdiameterwill be atrifle oversized. The oversize will usually be ofthe order of about 0.002 inches on the diameter.

The use of a taperfacilitates manufacturing each side part by a stamping operation because it is easier to get the part off the tool. Furthermore, the taper resists the tendency of the bearing bushes to pull out, because it exerts an inwardly and axially directed retentive force against the wall ofthe bearing bush thus opposing any tendency ofthe parts to separate.

The connecting rod is assembled simply by first aligning the bearing bushes on an assembly jig. One bush is pressed over one end, and one side part is turned over in the jig. Then the other side part is pressed on. The faces bear against one another, and the bearings are tightly held in precise adjustment.

The connecting rod is now accurately manufactured. The side parts are heldtogetherwithout cementing or fastening means. The rod is ready for use. It will be seen that this construction comprises merely two sleeves and two stamped side parts, and is inherently much less expensive than a standard connecting rod made from a machine forging.

Furthermore, materials resistantto heat and the conditions in an internal combustion engine can be used which can be relatively lighterthan conventional forging material. For example, these connecting rods can readily be made from 1010 mild carbon steel perhaps case-hardened and will therefore be lighter and certainly as strong as conventional connecting rods.

This invention is not to be limited by the embodimentshown in the drawing and described in the description which is by way of example and not of limitation, within the scope ofthe appended claims.

Claims (6)

1. Aconnecting rod for an internal combustion engine comprising a first and a second side part, each of said side parts having a central web, and a journal sleeve at each end; and a pair of bearing bushes each including a central bearing bore having an axis and an outside surfaces, said outside surface being an interference fit in a respective journal sleeve of both of the side parts, the two side parts being in face-to-face contactwith each otherwiththejournal sleeves embracing and holding the two bearing bushes with their axes parallel, said side parts being joined together only by means ofthe bearing bushes, and being secured to said bushes only by an interference fit therewith.

2. A connecting rod according to claim 1 in which the outer surfaces ofthe bushes are substantially cylindrical and the journal sleeves are internally tapered in a direction outwardly oftheir respective associated side parts, wherebythe interference fit is greaterfartherfrom the other side partthan closerto it.

3. A connecting rod according to claim 1 or claim 2 in which each central web includes a stiffener rig.

4. Aconnecting rod according to claim 5 in which said stiffener rib comprises an arched part extending toward the two journal pads.

5. Aconnecting rod according to claim 1 in which the side parts are metal stampings.

6. Aconnecting rod constructed substantially as hereinbefore described with reference to, and as shown in, Figures 4to 6 ofthe accompanying drawings.