GB2123115A

GB2123115A - Connecting rod of fibre-reinforced plastics material

Info

Publication number: GB2123115A
Application number: GB08316217A
Authority: GB
Inventors: Thomas Fischer; Bernd Bongers
Original assignee: Messerschmitt Bolkow Blohm AG
Current assignee: Airbus Defence and Space GmbH
Priority date: 1982-07-07
Filing date: 1983-06-14
Publication date: 1984-01-25
Also published as: JPH0438929B2; GB2123115B; JPS5926614A; GB8316217D0; FR2529972A1; FR2529972B1; DE3225324C1

Abstract

One rod end 2, is designed as a closed cylindrical bearing, and the other rod end, is designed as a split cylindrical bearing. Unidirectional fibre strands are combined into a loop which embraces the closed bearing cylinder 9 and extends in the longitudinal direction of the rod, providing two belts, bands or chords 7.1 shaped at the open rod end part 3.1 to provide a flange having bores 5 for connecting a bearing cover 3.2. In order to be able to dispense substantially with metal parts without diminution in strength, at the open rod end part 3.1 the loop 7 is split and at the free belt ends, directed radially outwards from the rod shaft 1 for the flange formation, it is combined with a bearing bracket 8 extending from one belt, band or chord end to the other and consisting of fibre strands and a pressure bar 10 fills the space between the closed bearing cylinder 9 and the bearing bracket 8 and consists at least of fibre strands in an orientation parallel to the longitudinal axis of the rod. <IMAGE>

Description

SPECIFICATION A connecting rod made of fibre-reinforced plastics material This invention concerns a connecting rod made of fibre-reinforced plastics material, the one rod end of which, for example for a piston pin or gudgeon pin, is designed as a closed cylindrical bearing and the other rod end of which, for example for a crank pin, is designed as a split cylindrical bearing consisting of an open half-shell-shaped rod end part with a complementary half-shell-shaped bearing cover, in which unidirectional strands are combined into a loop which embraces or forms a bight around the closed cylindrical bearing and which extends longitudinally of the connecting rod, and the two bands or chords of which, at the open rod end part, are formed into a flange having bores for connection of the bearing cover thereto.

In such a connecting rod, the crank pin bearing is, as is known, split for fitting reasons. The embodiment known from German Offenlegungsschrift No. 30 04 575 is provided with a metal jacket around a plastics core, in comparison with a corresponding fully-metal construction, so as to provide a considerably lower mass and this leads, particularly where used in high-speed piston engines, to quiet operation and improved efficiency. Among such criteria there exists, of course, the endeavour to dispense with any metal parts. The mere elimination of the metal jacket in the case of the known connecting rod, of course, inter alia no longer guarantees the necessary strength to withstand practical compressive and tensile forces. The remaining fibre loop, in itself only capable of withstanding tensile loading, would buckle under compressive loading.Moreover, such a composite structure, utilising a metal jacket inter alia as defining the outer shape of the fibre loop, of two materials of different modulii of elasticity has, under loading of the connecting rod, the result that the stiffer fibre material is the one that is predominantly loaded, i.e. the supporting metal jacket is not fully loaded.

The problem underlying the invention is to make it possible, in the case of a connecting rod of the kind referred to at the introduction hereof, substantially to dispense with metal parts without there being any diminution in the strength of the connecting rod.

To solve this problem, the present invention provides a connecting rod of the kind referred to in the introduction hereof, characterised in that, at the open rod end part, the loop is split to provide free band or chord ends, directed radially outwards from the rod shaft for form ing the flange and is united with a bearing bracket extending from band or chord end to band or chord end and comprising fibre strands extending in an orientation parallel to the direction of extent of the bracket and/or crosswise relative thereto, along with the incorporation or embedding of a pressure bar occupying or filling the space between the closed bearing cylinder and the bearing bracket and consisting of at least fibre strands in an orientation parallel to the longitudinal axis of the rod.

Accordingly the invention is not confined to a combination of a fibre loop with a rod, with a similar fibre construction, which by reason of its presence between the two bearings of the connecting rod ensures the pressure absorption capacity thereof. On the contrary, in this composite structure involving the fibre loop and the pressure bar, adequate strength against transverse forces acting under mass acceleration is achieved by the introduction of the bearing bracket.In this respect, the bearing bracket coupling the belt, band or chord ends of the fibre loop in an interlocking or fixed manner makes possible not only the separation of said ends and the dispensing with an endless design calling at the open rod end part involving multiple curvatures of the fibre loop (Note: in accordance with the aforementioned German Offenlegungsschrift, in view of the requirement for flat flange surfaces at the open rod end, a sheathing of appropriate outer contour is indispensible), but also space-saving and nevertheless effective reinforcement of the open rod head part against the bearing (or inside of the hole) pressure of the flange bores, preferably in the manner set out in sub-claim 3 appended hereto.

Finally, if a layer type of construction is employed, such as is defined in sub-claim 2, in accordance with that of the connecting rod known from German Offenlegungsschrift No.

29 51 112 and having an endless loop around two closed bearings, the transversepull absorption capacity of the loop belts can be considerably increased by shear or thrusttransmitting layers. The above, and the further developments defined in the remaining subclaims will be explained in more detail hereinunder with reference to an exemplified embodiment of the invention illustrated in the accompanying drawings, in which: Figure 1 is front view illustrating a connecting rod made of fibre composite material and split at one of the two rod ends, constructed in accordance with the invention; and Figure 2 is perspective view illustrating the connecting rod of Fig. 1 partly as an exploded view.

For use for example as a connecting member between a linearly-moving part (such as a piston, not shown) of a crank assembly and a crankshaft, the depicted connecting rod consists substantially of a rod shaft 1 having rod ends 2 and 3, designed as cylindrical bear ings, on the one hand for a piston pin or gudgeon pin (not shown) and on the other hand for a crank pin (also not shown). For fitting on the crankpin, the respective rod end 3 is divisible at a parting line perpendicular to the longitudinal axis of the rod, connection of an open half-shell-shaped rod end part 3.1 to a corresponding half-shell-shaped bearing cover 3.2 being established by way of bolts 6, preferably bolts having a smooth shank part at the head end of the bolt and a threaded portion at the end remote from the head, fitted into bores 5 (Fig. 2) in their flanges 3.3 and 3.4 respectively.

In order, in the case of such a conventional configuration of the connecting rod, to achieve a construction consisting of fibre composite material, such as carbon fibre in a synthetic resin matrix, whilst dispensing with metal without a diminution in strength, the main or shaft part of the connecting rod is provided with an open loop 7 of fibre strands of unidirectional orientation along the loop belts, bands or chords, 7.1 upon the partition whereof at the open rod end part 3.1 for the flange formation the free belt, band or chord ends are directed radially outwards as compared with the rod shaft 1. Positive locking in the open rod end part 3.1 between the free belt ends of the loop 7 is achieved by a bearing bracket 8 extending from belt end to belt end, also made of fibre strands of unidirectional orientation in the direction of the extent of the bracket.In this respect, incorporated in or embedded in the space between a bearing cylinder 9, which a bight of the loop extends and the bearing bracket 8, is a pressure bar 10 which is built up at least from unidirectional fibre strands parallel to the longitudinal axis of the rod and ensures the necessary pressure-absorptive capacity of the connecting rod. Through a thrust-transmitting (or shear-transmitting) intermediate layer 11 of fibre strands having a fibre orientation which is crosswise as compared with the bearing bracket 8 (fibre fabric, or layers) moreover adequate strength with respect to the bearing stress (or stress inside of the hole) of the flange bores 5 (Fig. 2) is ensured.For this purpose, intermediate layers of fibre fabric or layers with crosswise fibre orientation, can equally well be embedded in the undirectional fibre construction of the bearing bracket 8, as also the intermediate layer 11 can additionally have intermediate layers of fibre material in unidirectional orientation from belt end to belt end. The crosswise fibre orientation is preferably alternately + 45' and 0'/90" to the longitudinal axis of the bracket.

For flush embedding of a bearing shaft 1 2.1 which may, if necessary, be of metal, seated on the bearing bracket 8 in the region of the bolts 6 are, additionally, filling pieces 1 3 made of fibre fabric or layers, preferably in layers alternating with respect to the fibre orientation, of i: 45 and 0 /90 relative to the longitudinal bearing axis. At the closed rod end, in contrast, a bearing brass 14 is incorporated or embedded in the said bearing cylinder 9 which is united with the loop 7 and the pressure bar 10 and which consists of fibre material preferably in an orientation of 0 /90 to the longitudinal bearing axis.

To increase the thrust or shear stiffness of this fibre structure, there are finally, at the two rod end faces, cover layers or top or surface layers 15, as well as intermediate layers 1 6 parallel thereto, and subdividing the loop 7 with the bearing bracket 8, the pressure bar 10, the intermediate layer 11 and the filling pieces 1 3 in the bearing longitudinal direction, in each case made of fibre material preferably with + 45" orientation to the longitudinal axis of the rod. It is selfevident, moreover, that for all crosswise-orientated fibre material appropriate fabric or layup are usable.

As regards the bearing cover 3.2, the fibre structure thereof corresponds to that of the open rod end part 3.1 of the connecting rod, i.e. here an identical bearing bracket 1 7 having filling pieces 18 mounted in the region of the bolts 6 (for the bedding of a second bearing half 1 2.2 e.g. of brass) is united by way of an intermediate layer 1 9 of the aforedescribed kind with a further similar bearing bracket 20, which corresponds to the loop 7 of the main part of the connecting rod. Also corresponding thrust-transmitting surface and intermediate layers 1 5.1 or 16.1 respectively are present here.

Moreover, by means of shim blocks 21 and 22 associated with the heads or nuts respectively of the bolts 6 and having appropriate shaping or splicing, compressive stress peaks at the relevant bearing or contact surfaces are largely precluded. These shim blocks may, as is customary, consist of metal and, to improve the force transmission, be bonded on the flanges 3.3 or 3.4 respectively.

As illustrated more particularly by Fig. 2, the described connecting rod structure is a composite structure consisting of individual fibre component parts, which may be blanks or pre-forms from appropriate pre-shaped strand profiles, which may partly also be stamped parts. Thus the connecting rod can be produced in accordance with unitary constructional principles or mechanical assembly techniques, in other words it is particularly suitable for quantity production.

Claims

1. A connecting rod made of fibre-reinforced plastics material, the one rod end of which, for example for a piston pin or gudgeon pin, is designed as a closed cylindrical bearing and the other rod end of which, for example for a crank pin, is designed as a split cylindrical bearing consisting of an open halfshell shaped rod end part with a complementary half-shell-shaped bearing cover, in which unidirectional fibre strands are combined into a loop which embraces or forms a bight around the closed cylindrical bearing and which extends longitudinally of the connecting rod, and the two bands or chords of which, at the open rod end part, are formed into a flange having bores for connection of the bearing cover thereto, characterised in that, at the open rod end part, the loop is split to provide free band or chord ends, directed radially outwards from the rod shaft for forming the flange and is united with a bearing bracket extending from band or chord end to band or chord end and comprising fibre strands in an orientation parallel to the direction of extent of the bracket and/or crosswire relative thereto, along with the incorporation or embedding of a pressure bar occupying or filling the space between the closed bearing cylinder and the bearing bracket and consisting at least of fibre strands in an orientation parallel to the longitudinal axis of the rod.

2. A connecting rod as claimed in claim 1, characterised by rod-configured surface layers and intermediate layers parallel thereto and subdividing the loop, with the bearing bracket or a pressure bar, in the longitudinal direction of the bearing, in each case consisting of fibre strands in crosswise orientation.

3. A connecting rod as claimed in claim 1 or 2, characterised in that the bearing bracket, built up from fibre strands of unidirectional orientation extending in the longitudinal direction of the bracket, is connected, by way of an intermediate layer, consisting of fibre strands in an orientation which is crosswise as compared therewith, to the belt ends of the loop and the pressure bar.

4. A connecting rod as claimed in claim 1, 2 or 3, characterised in that a respective filling piece, each consisting of fibre strands in crosswise orientation is mounted on the bearing bracket, on the side facing the bearing cover in the region of flange bores.

5. A connecting rod as claimed in claim 1, characterised in that the closed bearing cylinder is built up in combination with the loop and the pressure bar comprises fibre strands in crosswise orientation, more particularly 0 /90 orientation to the longitudinal axis of the bearing.

6. A bearing cover of a connecting rod as claimed in any of the preceding claims, characterised by a fibre construction in accordance with that of the open rod end part in which the cover layer or bearing bracket corresponding to the loop of the connecting rod has the shape of the cover bearing bracket.

7. A connecting rod as claimed in any of claims 1 to 6 having a bearing cover of fibre construction corresponding to that of the open rod end part in which the cover layer or bearing bracket corresponds to the loop of the connecting rod has the shape of the cover bearing bracket.

8. A connecting rod substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.