GB2231638A - Manufacture of composite vehicle drive shafts - Google Patents

Abstract

In the manufacture of composite drive shafts, a plurality of cylindrical metal tubes (14) are coupled to one another in an end-to-end relationship by a plurality of joining plug members (42) to form a longitudinally extending series of metal tubes. The series of metal tubes are fed along a longitudinal axis to an apparatus for applying the individual layers of a composite fiber sleeve along with a curable resin material to the tube. As the series of tubes having the cured composite sleeve thereon exits the apparatus, the tubes are severed at each of the joining plugs (42) to produce a plurality of individual fiber reinforced tubular elements. <IMAGE>

Description

1 MANUFACTURE OF COMPOSITE VEHICLE DRIVE SHAFTS This invention relates

generally to the manufacture of fiber reinforced vehicle drive shafts.

over the past decade, there has been an ongoing endeavor by the industry to reduce the weight of vehicles in order to improve fuel economy. In addition to downsizing and redesigning vehicles to make the most efficient use of the available space, a great deal of attention has been given to constructing various vehicular components of lighter weight materials. For example, in the area of drive shafts, it has been proposed to replace conventional steel drive shafts with lighter weight aluminum tubes. However, depending on the length of the drive shaft, and the maximum, speed at which the drive shaft is to be rotated, vibration problems can arise.

While typically the tubular steel or aluminum drive shafts are adequate to transmit the torsional forces involved, there is a tendency for a shaft to "whip" or resonate mechanically when the shaft reaches a certain vehicle speed, typically referred to as a critical speed. Consequently, in order to overcome the critical speed limitations of single long drive shafts, typically multiple sections of shafts are employed. In these instances, adjacent individual drive shaft sections are connected to one another by means of a universal joint assembly which in turn is supported by a bearing mounting unit af.LI:i>:ed to the vehicle frame.

In order to accommodate a longer drive shaft such that the universal joint assemblies and the bearing mounting units can be eliminated, it has been proposed.tp-reinforce metal tubes with a fiber reinforced sleeve portion to 1 increase the axial stiffness of the shaft without substantially increasing its weight. For example, United States Patent Nos. 4,131,701; 4,173,670; and 4,214,932 all disclose fiber composite aluminum drive 5 shafts wherein aluminum tubes are wrapped with -alternating lay.!rs of resin-impregnated woven fiberglass cloth and resin-impregnated fiber reinforcing sheets. The reinforcing sheets are comprised of continuous unidirectional graphite fiber layers, with the graphite fibers arranged at angles between 5 to 201 with respect to the longitudinal axis of the tube. Another approach to reinforcing a tubular metallic drive shaft is disclosed in United States Patent No. 4,272,971, which discloses a drive shaft wherein the fiber reinforcing layer is applied to the inside surface of an aluminum tube.

While the above-discussed fiber-reinforced drive shafts have satisfactory operating characteristics, they have been found difficult and expensive to produce on a high volume production basis.

According to one aspect of the present invention there is provided a method of making a vehicle drive shaft comprising the steps of:

(a) providing a plurality of cylindrical metal tubes each having a longitudinal axis; (b) connecting the plurality'of metal tubes to form a longitudinally extending series of interconnected metal tubes; (c) feeding the series of interconnected metal tubes along a longitudinal path; (d) applying a reinforcing fiber layer around the outer surface of the interconnected metal tubes as the tubes travel in a longitudinal path; and (e) severing the series of tubes from one another to produce a plurality of individual fiber reinforced tubular elements.

For a better understanding of the present invention and to show how it may be carried into effect, reference will now be made, by way of example, 5 to the accompanying drawings, in which:

Fig. 1 is a side elevational view of a fiber reinforced composite tubular element of the present invention, shown for use as a drive shaft; Fig. 2 is a fragmentary sectional view taken along line 2-2 in Fig. 1 and showing the individual layers which constitute the preferred embodiment of the fiber composite sleeve; Fig. 3 is a schematic diagram showing one method of fabricating the fiber composite tubular element of the invention on a continuous basis wherein the fiber composite sleeve is formed and cured about a series of individual metal tubes temporarily joined together and moving in a longitudinal path; and Fig. 4 is a side elevational view of a composite fiber reinforced tubular element produced according to the method schematically illustrated in Fig. 3.

1 Referring now to Fig. 1, there is shown a drive shaft 10 which utilizes a composite tubular element embodying the features of the present invention. The drive shaft 10 includes an outer composite fiber reinforcing sleeve 12 which surrounds and is attached to the exterior of a cylindrical metal tube 14. As illustrated, first and second connecting members 16 and 18, which are shown as yoke portions, are connected to opposite ends of the metal tube 14 for coupling the drive shaft between a drive member (not shown) and a driven member (not shown). While the connecting members are shown as yoke portions for connection to an associated universal joint assembly (not shown), it will be appreciated that other types of connecting members such as, for example, a splined shaft end can be used.

The connecting members 16 and 18 are typically secured to the ends of the metal tube 14 by a welding operation. To prevent heat damage to the composite sleeve 12 when the connecting members are attached, the ends of the reinforcing sleeve 12 are spaced inwardly from the ends of the metal tube 14 to provide exposed metal end portions 20 and 22. As will appear more fully below, in the preferred method of manufacture, the reinforcing sleeve 12 is initially formed along the entire length of the metal tube 14 and is subsequently stripped from the end portions 20 and 22 by severing it circumf!rentially with a saw, and peeling it off. In other methods of manufacture, the reinforcing sleeve 12 is formed so that it initially does not cover end portions 20 and 221.

Turning now to Fig. 2, there is shown a cross-section through the tube 14 and the preferred embodiment of the 1 composite reinforcing sleeve 12. Typically, the metal tube 14 is a cylindrical aluminum tube fabricated in a conventional manner. The length, diameter, and wall thickness of the tube, along with the particular aluminum alloy from which the tube is formed, may vary from application to application, depending on the particular power transmission requirements of the drive shaft. In any event, the use of the composite reinforcing sleeve 12 having the specific construction of the present invention has been found to sufficiently increase the axial stiffness ---ofthe aluminum tube such that weight of the tube can be substantially reduced as compared with a tubular aluminum drive shaft without the reinforcing sleeve.

The composite reinforcing sleeve 12 basically consists of three sections: an isolation layer 32, a fiber reinforcing layer 34, and a covering layer 36. As will be discussed, in the preferred method of manufacture, the individual layers of the sleeve 12 are bonded to one another and the tube by a vinylester resin.

The isolation layer 32 includes individual layers 32a, 32b, and 32c. The first isolation layer 32a is composed of a plurality of longitudinally extending threads of string material ecually snaced about the circumference of the tube. This layer is not essential to the functioning of-- the invention but, as will be discussed, is provided as a visual indicator to avoid contact of a saw blade (not shown) with the metal tube 14 when striping the end portions of the reinforcing sleeve 12 as previously described. In the preferred embodiment of the drive shaft, the laver 32a consists of eight longitudinally extending polyester strings equally spaced about the circumlerence of the tube.

The second isolation 2a%er 3.2b is composed of individual strips of' a screen-like cloth material which extend lonQitudinal',,, and have overlapping lateral edge portions to co=.,-,letel,,, surround the tube. This layer functions to isolate the fiber reinforcing layer 34, which is typically graphite, from the aluminum tube 14, since it has been found that direct contact between graphite and aluminum results in undesirable electrolytic corrosion. The exact width of the individual strips will be dependent on the number of strips utilized, along with the outside diameter of the tube. While the number of strips of cloth material which are utilized to surround the tube can vary from application to application, in the preferred embodiment, four individual strips of cloth material are utilized.

The third isolation layer 32c is similar to the first layer 32a, and is comprised of a plurality of longitudinally disposed threads of polyester string uniformally spaced about the circumference of the tube. In the preferred embodiment, eight threads are used. Again, this is not an essential layer, but is provided to form and hold the strips of cloth material in place on the metal tube 14. It will be appreciated that, while the isolation string layers 32a and 32c are shown in Fig. 2 as spacing the isolation cloth layer 32b from both the tube 14 and the fiber reinforcing layer 34, there is actually contact between the layer 32b and the tube 14 and between the layer 32b and the reinforcing layer 34 in the regions between the spaced apart longitudinally extending threads.

The fiber reinforcing layer 34 is typically comprised of graphite and includes a plurality of individual and independent reinforcing fiber strands or "tows" which are preferably located parallel to the lonaitudinal axis of the tube, and uniformly positioned about the isolation layeir 32. Each tow consists o-f- a predetermined number of longitudinally disposed, individual graphite fibers. The exact number oil tows of graphite which& are utilized will depend on the number of individual ilibers located in each tow and the overall amount of reinforcing which is desired. in one 1 preferred embodiment, 115 longitudinally disposed tows of graphite fibers are utilized, with each tow being composed of 36,000 individual fibers of graphite.

The covering or protective layer 36 includes individual layers 36a, 36b, and 36c, and functions as a means for retaining the longitudinal graphite strands of the layer 34 adjacent the metal tube 14. The first covering layer 36a is comprised of a circumferential wrapping of fiberglass strands. The number of circumferential wrappings per given length of the tube will be dependent on the amount of graphite which has been applied to the tube, along with the number of individual glass fibers included in each strand. In the preferred embodiment, each strand is composed of 1,800 fibers of fiberglass, and is wrapped about the tube to produce twenty wraps per longitudinal inch.

The second covering layer 36b is another circumferential wrapping, similar to that of the first covering layer 36a, but with polyester string, of a type similar to that used in the first and third isolation layers 32a and 32c. It should be noted that the layers 36a and 36b, although illustrated as overlying layers, do not visually form separate layers, since the strands of one wrapping will typically fall in between the strand of the other, so that layers 36a and 36b appear visually as a single layer.

The third covering layer 36c, which is the outermost layer of the sleeve 12, is applied similar to and is identical in material characteristics to that of the isolation layer 32b, and provides an outer cloth covering which produces a smobth out-er surface on the drive shaft.

Turning now to Fig. 3, there is shown schematically an apparatus 40 for forming composite tubular elements of the type illustrated in Fig. 2 and a continuous basis. As shown in Fig 3, a plurality of metal tubes, shown as 14a, 14b, 14c, 14d, are interconnected in an end-to-end -8relationship by a plurality of plug members 42. The plug members 42, which typically are constructed of a plastic material, are shown as double-ended, with a centrally located protruding annular flange portion 44 having an outer diameter greater than the outside diameter of the tubes. As will be discussed, the protruding flange portion 44, after each layer of the composite sleeve has been applied and cured on the tubes, provides an annular raised portion in.the sleeve which functions as a visual reference to define the specific location at which the tubes must been sawed apart.

The apparatus 40 includes a plurality of individual application stations which, as discussed in more detail below, are utilized to apply the various materials required is to form the composite fiber sleeve on the aluminum tube. The apparatus also includes a pair of pulling rollers 46 and 48 for pulling the longitudinally extending series of tubes through the apparatus along a longitudinally extending path at a predetermined speed.

As shown in Fig. 3, at first station 50, the first isolation layer 32a of longitudinally extending, circumferentially spaced apart string is applied. String from a plurality of rolls 52 passes through a guide means 54 and an application means 56, which may be pulleys or Ehe like, into place on the tube 14. Although four rolls are shown, eight rolls are used in the preferred embodiment of the invention. Also, while shown as tapered rolls or spools, the spools used are preferably of the center- feed type, so that the last turn is on the outside, and additional rolls can be connected without interrupting the process.

Then, at a second station 58, the second isolation layer 32b of strips of cloth material is applied. As shown, the layer 32b is applied in four segments. At the second station 58, the material of the second layer 32b is applied from rolls 60 and 62. While not shown in the r -9drawings, the rolls 62 are preferably located along a line which is perpendicular to the line along which the rolls 60 are located. The individual strips are urged into conformance with the shape of tube 14 by a conical 5 preformer 64.

Next, at a third station 66, the third isolation layer 32c of string is applied to form the cloth layer 32b around the tube 14. As with the first station 50, the string from a plurality of rolls 68 passes through a guide means 70 and an application means 72 into position around the tube 14.

At a fourth station 74, approximately half of the fiber reinforcing layer 34 is applied. A set of rolls 76, although shown as six in number for simplicity, actually number approximately half of the total number of graphite tows to be applied. The tows supplied from the rolls 76 pass through individual apertures in a forming ring 78 into conformance with the shape of the tube 14. Then, at a fifth station 80, a resin mixture is supplied from a tank 82 through a line 84 to a dispensing end 86, from which it coats the first half of the fiber reinforcing layer 34 and the underlying isolation layer 32.

The resin mix contained in the tank 82 is preferably a vinylester resin mix of the type available under the trade name Derakane. A suitable resin mixture is available from Dow Chemical of Joliet, Illinois under part number 411-35. In addition, any conventional resin mixture may be used, although it should be selected from among those that remain flexible after curing. Although not shown in the drawings, a catalyst or hardener can be mixed with the resin mixture shortly before application of the mixture to the partially formed sleeve.

At a sixth station 8S, the remainder of the desired number of graphite tows are applied from a set of rolls 90 through a formina rinc 92 into conformance with the tube 14 and, at a seventh station 94, are again coated with the -10resin mixture from the tank 82, through a line 96 and a dispensing end 98.

An eighth station 100 and a ninth station 102 include a spinner head 104 having rolls 106 and 108 for circumferentially wrapping covering layers 36a and 36b respectively. Of course, more than one such spinner head 104 may be provided, and more than a single roll can be used to apply the layers 36a and 36b. As illustrated, the head 104 contains the fiberglass material of the first covering layer 36a on the roll 106 and the polyester string material of the second covering layer 36b on the roll 108. As previously described, the layers 36a and 36b are circumferential wrappings which, in the preferred embodiment, are applied at a rate of approximately twenty per inch. At a tenth station 110, the resin mix from the tank 82 is again applied, through a line 112 and a dispensing end 114.

Then, at an eleventh station 116, the final layer, the third covering layer 36c, is applied. A set of rolls 118 contain cloth material identical to that contained by the rolls 60, which material is urged into conformance with the tube 14 by a conical performer 120. A set of rolls 122 contain cloth material identical to that contained on the rolls 62, which material is urged into conformance with t-he tube 14 by a conical entrance 124 of a heated forming die 126. As was the case with the rolls 60 and 62, the rolls 118 and 122 are preferably located along lines perpendicular to one another. The forming die 126 not only forms the surface of the continuous drive shaft assembly, but also provides appropriate heat input to effect a rapid cure o..;' the resin mixture as the series of drive shafts are pulled through the apparatus 40.

The continuous chain of composite tubular elements 10 is the- cut apart at pro4-ru,-'-nc flange portions 48, and stripped in a manner as described above to form exposed metal end portions 20 and 2-2, to which appropriate connecting members can be attached by conventional welding.

The composite tubular element produced by the method of Fig. 3 is shown in Fig. 4 prior to the attachment of the connecting members.

it will be appreciated that other methods can be utilized to produce a fiber-reinforced aluminum drive shaft embOdying the principal featuresof the present invention.

For example, Fig. 5 schematically illustrates a method wherein a stiff, performed, precut and previously cured reinforcing sleeve 130 of a predetermined length is provided, with an internal diameter slightly larger than the external diameter of the metal tube 14. As illustrated in Fig. 5, the reinforcing sleeve 130 is slipped into position over a metal tube 132, to which a layer of glue 134 has been applied.

various types of glues or bonding agents may be used for the glue 134. One such structural adhesive which can be used is commercially known as Metalbond 1133, and is an elastomer modified epoxy material sold by the Narmco division of Celanese Corp, New York, New York. Such adhesives may be applied by brushing or spraying.

In accordance with the provisions of the patent statutes, the composite tubular element of the present invention, alona with the methods of producing the tubular elemen-k, have been illustrated and described in its preferred embodiments. However, it will be appreciated that numerous modifications and variations of the disclosed invention will be apparent to one skilled in the art, including re-arrangement in the ordering of layers and the addition or omission of layers, and may be made without departing from the scope of the attached claims.

The vehicle drive shaft and manufacturing method disclosed herein are also described and claimed in our copending patent applications Nos. 8708016 and 90 (Serial Nos. 2189862 and is

Claims (6)

1. A method of making a vehicle drive shaft comprising the steps of:

(a) providing a plurality of cylindrical metal tubes each having a longitudinal axis; (b) connecting the plurality of metal tubes to form a longitudinally extending series of interconnected metal tubes; (c) feeding the series of interconnected metal tubes along a longitudinal path; (d) applying a reinforcing fiber layer around the outer surface of the interconnected metal tubes as the tubes travel in a longitudinal path; and (e) severing the series of tubes from one another to produce a plurality of individual fiber reinforced tubular elements.

2. A method according to claim 1, wherein the cylindrical metal tubes are connected together end-to- end by a plurality of joining plug members.

3. A method according to claim 2. wherein the plug members are made from plastics material.

4. A method according to claim 2 or 3, wherein each plug member is doubleended and has a central flange portion.

5. A method according ot claim 4, wherein the central flange portion has an outer diameter greater than the outside diameter of the metal tubes.

6. A method according to claim 1 or 2, including, subsequently to the step of severing the. tubes, the step of stripping a selected portion of the fiber reinforced sleeve from at least one end of each tubular element to provide an exposed metal end surface.

Published 1990 at 71HigviHolborr..LendonWC1R4TP Ftrtherec)Plesmkvbe obtained froin The Patent Office.

SaleS BrancII. St Mary Cray. Orpington, Kent BR5 3RD Printed by Multiplex techniques ltd. St Mary Cray. Kent. Con. 1187 W