AU611968B2

AU611968B2 - Connecting rods

Info

Publication number: AU611968B2
Application number: AU25521/88A
Authority: AU
Inventors: John Devine
Original assignee: UK Secretary of State for Trade and Industry
Current assignee: UK Secretary of State for Trade and Industry
Priority date: 1987-10-19
Filing date: 1988-10-19
Publication date: 1991-06-27
Anticipated expiration: 2008-10-19
Also published as: JPH03500802A; KR890701910A; DK86690D0; ES2011156A6; GB2229792A; AU2552188A; BR8807756A; GB9008305D0; GB8724466D0; WO1989003940A1; PT88790B; EP0444020A1; PT88790A; DK86690A; GB2229792B

Description

OPI DATE 23/05/89 APPLN. ID 25521 88

PCT

AOJP T EA9 6/ PC UMBER PCT/GB88/00881 INTERNATIONAL APPLl uO n UiO, a iC riL ij i a i-n 1 YI BUY (51) International Patent Classification 4 F16C 7/02 Al (II) International Publication Number: (43) International Publication Date: WO 89/ 03940 5 May 1989 (05.05.89) (21) Int'rnational Application Number: PCT/GB88/00881 (22) International Filing Date: 19 October 1988 (19.10.88) (31) Priority Application Number: (32) Priority Date: (33) Priority Country: 8724466 19 October 1987 (19.10.87) (74) Agent: BECKHAM, Robert, William; Ministry of Defence, Procurement Executive Patents IA(4), Room 2014, Empress State Building, Lillie Road, London SW6 ITR (GB).

(81) Designated States: AT (European patent), AU, BE (European patent), BR, CH (European patent), DE (European patent), DK, FR (European patent), GB, GB (European patent), IT (European patent), JP, KR, LU (European patent), NL (European patent), SE (European patent), US.

Published With international search report.

(71) Applicant (for all designated States except US):THE SE- CRETARY OF STATE FOR TRADE AND INDUS- TRY IN HER BRITANNIC MAJESTY'S GOV- ERNMENT OF THE UNITED KINGDOM OF GREAT BRITAIN AND NORTHERN IRELAND [GB/GB]; 10-18 Victoria Street, London SWIH OET

(GB).

(72) Inventor; and Inventor/Applicant (for US only) GB]; Castilla, Cilcain Road,.

Clwyd (GB).

*DEVINE, John [GB/ ,itymwyn, Nr, Mould, (54)Title: CONNECTING RODS (57) Abstract A connecting rod has an FRP backbone (11) in which fibres are continuous and subtantially longitudinally aligned. At least one of a big (20) and a little (32) end is formed from short fibred FRP, the short fibres being randomly aligned. The end material is bonded to the material of the backbone.

32- I -11 -13 I I II I II I I Ii

SII

22 WO 89/03940 PCT/GB88/00881 1 CONNECTING RODS The present invention relates to connecting rods particularly of the type used for connecting pistons to crank shafts in machines such as internal combustion engines.

Conventionally connecting rods are made from metal. A significant proportion of the power developed by an engine in use is effectively wasted as a result of the power required to drive the connecting rods themselves. There is therefore a great incentive to reduce the weight, and therefore the inertia, of connecting rods. In recent years the development of Fibre Reinforced Plastics (FRP) in which fibres of, for example, glass, carbon or boron are embedded in a plastic such as, for example, epoxy, polyester and vinyl-ester resin, polyamide, polyimide, PEEK (polyetheretherketone), PES (polyethersulphone), and polyetherimide, has resulted in considerable interest in their use for connecting rods. The use of FRP materials can potentially provide connecting rods having the requisite strength and a much reduced weight. Despite the potential advantages of using FRP, and the amount of work that has been expended in attempting to develop FRP connecting rods, there are as yet no FRP connecting rods in commercial service.

One of the problems which arise in the successful construction of a FRP connecting rod is the attachment of the connecting rod to the piston and the crank shaft. The end of the connecting rod connected to the piston is commonly known as the little end, whilst that connected to the crank shaft is commonly known as the big end. It is the big end connection which poses the most problems. Connecting rods are conventionally split at the big end along a diagonal of a hole which is designed to surround the crank shaft, the diagonal being at right angles to the axis of the connecting rod. Connection of the main body of the connecting rod to a detachable cap is usually effected by means of nuts and bolts. However in the design of a FRP connecting rod it is usual to have fibres in the FRP material aligned substantially longitudinally to the connecting rod axis as the main stresses therein are tension and, particularly, in compression. In consequence the holes drilled at the big end of the connecting rod to allow passage of a bolt lie substantially parallel to the adjacent fibres. The nut and bolt combination results in a shear effect, and FRP materials have low strength to shear forces parallel tothe alignment of the fibres therein. Various methods have been tried to overcome this problem, iL i *1* i PUT/GB 88/00 88 1 1 2 February 1990 I C9_ PO such as, for example, the combined use of FRP and metal for the manufacture of connecting rods, the incorporation oC metal inserts at the big end, angling out of the fibres at the big end so that 'the bolt holes pass through the fibres at right angles to the fibre alignment (resulting usually in an unacceptable width of the big end), and the use of fork type attachments with legs extending beyond the radial depth of the cap with a nut and bolt combination normal to the connecting rod axis and passing through the legs.

The present invention provides a novel form of FRP connecting rod.

According to the present invention a connecting rod includes a backbone formed from continuous fibred Fibre Reinforced Plastic, at least a substantial proportion of the continuous fibre being unidirectionally aligned along the length of the backbone, and a big end portion having a semi-circular channel and holes through which can be passed bolts whereby a cap can be secured to the big end portion, characterised in that the big end portion is formed from short-fibred Fibre Reinforced Plastic which surrounds the holes, the short fibres having random alignment and the material of the big end portion being bonded to the material of the backbone.

The use of short fibred Fibre Reinforced Plastic in big bnd portions has been taught in JP-A-5894620, Patent Abstracts of Japan, vol 7 no 193(M-238) (1330), which aims to provide a big end v1hich oes nzt need a bush. Long fibres are aligned along the length of the rod and along the peripheries of the big and little end holes. In the region of the holes short fibres are arranged and laminated at random with the intention of improving wear resistance. The Fibre Reinforced Plastic constituent of the big end portion remains of the long fibre variety, the short fibred variety being positioned only in the vicinity of the big end bearing holes not in the vicinity of the holes for the big end cap attachment bolts.

The backbone will usually be so shaped as to provide a degree of stiffness against bending and twisting, and a preferred embodiment has a backbone consisting of 2 channel sections bonded together along the bases of the channels.

United Ki.~dom Patont Office SUBSTITUTE SHEET PCT Intcrnational Application PCT/GB 88/00 8 81 29 December 1989 2A The materialsof the end and of the backbone are preferably bonded together by an injection moulding process. The bonding together of two channel sections to form the backbone, and of the backbone to the end, may be performed in one process.

In one method of forming an embodiment of the invention 2 identical channel sections are formed from continuous fibred FRP by sandwiching a sheet of FRP between 2 thin metal sheets, the FRP sheet being aligned such that a substantial proportion of the fibres will lie along the length of the channels, the sandwich being then heated to an appropriate temperature and forced against a first mould by air pressure, the channels then being bonded together at the base of the channel sections, the resultant backbone being positioned relative to a second mould defining the shape of a big end, short fibred FRP material then being injected into the end mould such that the S LTIE SHEET [fUnited Kingdom Paltnt Ofice PCT International Application.

-I-

WO 89/03940 PCT/GB88/00881 3 material bonds to the material of the backbone.

Both ends of the backbone may be treated, at the same time with the backbone being positioned in a mould defining the final shape of the rod, and injecting short fibred FRP at both big and little ends.

The FRP materials are preferably thermoplastic materials and might be, for example, polytheretherketone (PEEK). A suitable material is Fiberite (RTM) APC2 manufactured by the Fiberite Company, and a suitable short fibred material is Victrex (RTM) manufactured by ICI plc, which is available with varying percentages and types of fibre reinforcement.

One embodiment of the invention and one method of making the embodiment will now be described, by way of example only, with reference to the accompanying drawings, of which Figure 1 is an elevation of a connecting rod, Figure 2 is an end elevation, in section along line II-II of Figure 1, of the connecting rod, Figure 3 is a plan view, in section along line III-III of Figure 1, Figure 4 is a perspective view of an apparatus for making a backbone member for the connecting rod illustrated in Figures 1 to 3.

Figure 5 is a plan view of a backbone member, Figure 6 is an end view of a backbone member, and Figure 7 is a perspective view c.f an apparatus for bonding a piston end member to the backbone member.

A connecting rod (Figures 1 to 3) 10 has a backbone 11 formed from 2 channel members 12, 13 each formed from continuous fibred FRP material, the continuous fibres being substantially unidirectionally aligned with a centre line 14 of the connecting rod. Each channel member 12, 13 (see Figure 3) has a base 15, sides 16, and flanges 17.

The flange members 17 are extended as illustrated in Figure 1 at 18 in the vicinity of a first end of the backbone 11. A big end portion formed from short fibre FRP is bonded to the end 19 of the backbone 11, the bonding extending over the extensions 18 of the flanges 17.

A semi circular channel 21 is symmetrically positioned with reference to the centre line 14 at the first end 19 of the backbone 11. The big end portion 20 is connected to a cap portion 22, which defines

A

7 WO 89/03940 PCT/G B88/00881 a semi circular channel 23 complementary with the semi circular channel 21, by bolts 24 passing through holes (not shown) in end portion and cap 22 and nuts A second end 30 of the backbone 11 which has extensions 31 of the flanges 17 has a little end portion of short fibre FRP, 32, bonded thereto.

The little end portion 32 and backbone 11 have a hole 33 there through, the centre line of the hole 33 passing through the axis 14 of the backbone 11.

A connecting rod as described above with reference to Figures 1 to 3 can be produced (Figures 4 to 7) by sandwiching a sheet of continuous fibred FRP 40 between 2 thin sheets 41 of a metal such as aluminium and forcing the sheet by, for example, air pressure (as illustrated at 42) into a channel 43 in a die 44. The alignment of the fibres in the sheet 40 should be such that they lie substantially longitudinally along an axis of a channel member (Figures 5, 6) that is formed. The channel has a base 15, sides 16 and flanges 17.

Extensions 18, 31 are formed on the flanges 17, either by machining oversized flanges, or by shaping of the sheet 40. A backbone 11 is formed (Figure 6) by bonding the bases 15 of 2 identical channels together.

An end member 20, or end 32 is attached at an end 19 or 30 by positioning the end within a mould box 50 (Figure 7) having a mould to form the appropriate end shape, and injecting short fibre FRP through an aperture 51. By keeping the mould atthe appropriate temperature the materials of the backbone 11 and end members will be bonded together.

The connecting rod may be formed in one operation by positioning the channel members in a mould defining the shape of the final rod, and simultaneously bonding bases 15 of the channel members together and injecting short fibre FRP into big 20 and little 32 end mould boxes similar to box ~1_11 WO 89/03940 PCT/GB88/00881 A connecting rod according to the invention,in which the backbone was formed from Fiberite (RTM) APC2 and the end members from Victorex (RTM) having a 30% carbon fibre reinforcement was constructed and tested. The end members for the test specimen were assembled by machining material from block end members to fill the channels in a backbone such as that illustrated in Figures 5 and 6, and the two were then bonded together by heating and the application of pressure. The connecting rod was used in an engine running at various speeds ranging from 1,500 to 3,000 rpm at minimum load, and survived 3 x 106 cycles without any signs of fatigue cracking,even about the bolt holes or neck regions of the assembly.

I

Claims

1. A connecting rod including a backbone formed from continuous fibred Fibre Reinforced Plastic, at least a substantial proportion of the continuous fibres being unidirectionally aligned along the length of the backbone, and a big end portion having a semi-circular channel and holes through which can be passed bolts whereby a cap can be secured to the big end portion, characterised in that the big end portion is formed from short-fibred Fibre Reinforced Plastic which surrounds the holes, the short fibres having random alignment and the material of the big end portion being bonded to the material of the backbone.

2. A connecting rod as claimed in claim 1 characterised in having also a little end formed from short fibred FRP.

3. A connecting rod as claimed in any one of claims 1 to 2 characterised in 15 that the backbone consists of two channel members bonded together along bases of the channels.

4. A method of forming a connecting rod characterised in that two identical channel members are formed from continuous fibred FRP by sandwiching a sheet of FRP between two thin metal sheets, the FRP sheet being aligned such 20 that a substantial proportion of the fibres will lie along the length of the channels, the sandwich being then heated to an appropriate temperature and forced against a die by pressure, the channel members then being bonded together at bases of the channel sections, the resultant backbone being positioned relative to a first mould box defining the shape of a big end portion S 25 having holes through which can be passed bolts, short fibred FRP material then being injected into the mould box such that the material bonds to the material of the backbone.

A method of forming a connecting rod as claimed in claim 4 characterised in that the backbone is also positioned relative to a second mould box defining the shape of a little end into which short fibred FRP material is injected.

6. A method of forming a connecting rod characterised in that two identical -4910313,arsdat.097,25521.com, I -7- channel sections are formed from continuous fibred FRP by sandwiching a sheet of FRP between two thin metal sheets, the FRP sheet being aligned such that a substantial proportion of the fibres will lie along the length of the channels, the sandwich being then heated to an appropriate temperature and forced against a die by pressure, the channel sections then being positioned in a mould box defining the shape of the connecting rod and being bonded together at bases thereof whilst simultaneously short-fibred FRP is injected into ends of the mould defining big and little ends.

7. A method of forming a connecting rod as claimed in any of claims 4 to 6 characterised in that the sandwich is forced against the die by air pressure.

8. A connecting rod characterised in being formed by a method according to any one of claims 5 to 7.

9. A connecting rod as claimed in claim 8 characterised in having holes in the big end portion through which can be passed bolts. 15

10. A machine characterised in including a connecting rod according to any one of claims 1 to 3 or claim 9, the connecting rod having a cap portion secured to the big end portion by the bolts passing through the holes in the big end portion and holes in the cap portion and by nuts.

11. A connecting rod substantially as hereinbefore described with reference to the accompanying drawings.

12. A method of forming a connecting rod substantially as hereinbefore described with reference to the accompanying drawings. Dated this 13th day of March, 1991. DAVIES COLLISON Patent Attorneys for THE SECRETARY OF STATE FOR TRADE AND INDUSTRY IN HER BRITANNIC MAJESTY'S GOVERNMENT OF THE UNITED KINGDOM OF GREAT BRITAIN AND NORTHERN IRELAND 910313,arsdat.097,25S21om,2