GB2127938A

GB2127938A - Method of forming a composite drive shaft tube

Info

Publication number: GB2127938A
Application number: GB08324339A
Authority: GB
Inventors: Leon W Valencic; Barry L Zackrisson
Original assignee: Dana Inc
Current assignee: Dana Inc
Priority date: 1982-09-29
Filing date: 1983-09-12
Publication date: 1984-04-18
Also published as: KR840006157A; GB8324339D0; MX157143A; GB2127938B; JPS5983620A; BR8305331A; DE3331789A1

Abstract

A method is disclosed for forming a drive shaft by bonding a metallic drive shaft operating member, such as a tube yoke 14, directly to a composite tube 12 of fibre-reinforced resin, with the composite tube having been cut to size from a multiple length composite tube. A taper is formed in the end of the tube and a taper is formed on the end of the metallic member adapted to be inserted into the tube. An adhesive containing glass beads 28 of a selected diameter for controlling the bond line thickness and spacing the tapers between the composite tube and the metallic member is applied to the taper on the metallic member. The metallic member is then securely axially inserted into the tube with a circumferential twisting movement to obtain a controlled bond line. The adhesive is then cured to form a drive shaft. <IMAGE>

Description

SPECIFICATION Method of forming a composite drive shaft tube Background of the Invention 1. Field of the Invention: This invention relates to composite drive shafts having a hollow fiber reinforced resinous shaft body and more especially to the attaching of the ends of such a shaft body to metallic drive shaft members.

2. Description of Prior Art: In the prior art, attachment of a composite drive shaft tube to a metallic drive shaft member, such-as for example a metallic yoke of a Cardan type drive shaft assembly, has been attempted by many methods, none of which lend themselves to the high speed, production line potential of the instant invention.

In a great number of prior art methods, for example, as disclosed in U.S. patent 4,236,386 issued to Yates and Presta on December 2, 1980, the tubular fiber reinforced portion or composite tube has the end thereof secured to an intermediate metal sleeve in a driving relationship through the provision of an irregular surface on the intermediate metallic sleeve which forms a bonded interlocking driving conection with the tubular fiber portion. A similar bonded interlocking driving connection is shown in U.S. patent 4,238,540 issued to the aforementioned Yates and Presta on December 9, 1980. In both of these patents the metallic intermediate sleeve is then welded to a drive shaft member, such as a metallic yoke. A U.S. patent 4,190,479 issued to Derek R.Smith on February 26, 1980 discloses bonding a fiber reinforced tubular shaft to an end yoke; the yoke having a pair of spaced cylindrical walls defining an annular groove into which is received the tube end in a bonded relationship.

While the tube need not be manufactured to a particular length, but may be subsequently cut to desired length, the yoke is expensive and difficult to manufacture. Other prior art methods, as shown in U.S. patent 3,553,978 issued to Wiliams on January 12, 1971, disclose winding the fiber reinforced resinous tube directly onto an irregular surface of a yoke member.

In all of the above disclosures, the tubular fibrous portion must be specifically manufactured for the shaft being assembled, particularly as to length or else the metallic portion must be of a difficult configuration to manufacture.

U.S. patent 4,256,412 issued to Gerd Tybus and Helmar Laube on March 17, 1981 discloses a composite rod with a tapered end bonded to a transitional element, however, it appears the rod was custom manufactured to size requirements and not cut from multiple length rod. Additionally, the reference does not disclose spacing members in the bonding material.

Summary of the Invention The present invention contemplates a method for making drive shaft assemblies including a composite drive shaft tube portion, wherein the composite driveshaft tube is directly bonded at least at one of its ends to a drive shaft member such as a metallic tube yoke. To accomplish this method of assembly in an economical and expeditious manner, the composite tube portion is obtained from an elongated one-piece tube member. The latter is manufactured with its length great enough to manufacture more than one drive shaft tube for more than one drive shaft assembly.

To this composite drive shaft tube is ultimately bonded a simple metallic drive shaft member, as opposed to the above referred to prior art disclosures where either the tubular portion must be manufactured to a specific length or expensive metallic yokes utilized.

The elongated one-piece composite tube member can be cut to length as needed greatly reducing the requirement for a variety of tubes prefrabricated to a variety of required lengths.

The inner diameter at the end of the composite tube is then machined to a conical taper in the range of 1 to 5 relative to the longitudinal axis of the tube, with the larger diameter end of the taper being at the open end of the tube. The mating external surface of the metallic drive line member is machined with a matching taper so that the metallic member may be inserted into the tube, with the inserted end being the smaller end of the taper. This taper should correspond with the tube's taper and be in the range of .001 to .005 inches (.025 to 0.23mm). The length of the taper overlap of the composite tube and the metallic member is dimensioned to provide an adequate safety factor relative to torsional lap shear when the two members are bonded as hereafter described.An epoxy resin can be used as the bonding agent to bond the metallic member to the composite tube and should include means to insure that when the taper on the metallic member is inserted into the mating taper of the tube member, bonding material of sufficient thickness should be present in the entire bonding area. Such means can be small substantially spherical spacing members with substantial compressive strength mixed with the bonding agent to insure a space exists between the metallic member and the tube and that excessive spaces does not exist. By controlling the size of the spherical members, which, in the preferred embodiment, are glass beads, the radial and longitudinal space between the two mem bers can be controlled. This will also control the straightness of the shaft assembly.

Brief Description of the Drawings Figure 1 is a longitudinal view, partly in longitudinal cross section of a portion of a drive shaft formed in accordance with this invention; and Figure 2 is an enlarged cross sectional view taken along the lines 2-2 in Fig. 1 with the mating angle and the space between the composite tube and the mating metallic element exagerated for clarity purposes as well as the bonding material being exagerated in size.

Description of a Preferred Embodiment A drive shaft according to the present invention is shown fragmentarily at 10 and includes a cylindrical composite drive shaft tube 12 connected to a conventional Carden type tube yoke 14, by bonding in a manner according to this invention.

The composite drive shaft tube 12 can be purchased from several vendors, and to practice this invention is purchased in lengths sufficiently long enough so that it may be cut to shorter lengths to make more than one shaft 10 acording to this invention.

Two vendors (there may be others) who can supply such tubing are Hercules Incorporated of Wilmington Delaware, U.S.A. and Shakespear Products Division of Kalamazoo, Michigan U.S.A.

The tube 12 has an inner layer 16 of fiberglass which is referred to as "E" glass type 30 and is made by wrapping fiberglass about a suitable mandrel which fibers reinforce a thermosetting resin matrix in which they are wound to give the necessary properties of strength and durability to the tube.

These glass fibers are wound at angles of approximately j 45' relative to a line parallel to the longitudinal axis of the tube 12. The glass fibers are the main carrier of torsional loads on the tube 12. Upon the layer 16 of fiberglass, there is placed a layer of carbon graphite fibers 18 which circumferentially surrounds the fiberglass layer and are also embedded in a matrix of thermosetting resin which bonds to the external periphery of the fiberglass layers 16.

The carbon graphite fibers 18 extend substantially longitudinally of the tube 12 and are for the purpose of imparting stiffness to the tube 12. To the extent that the graphite fibers may deviate from being exactly longitudinal of the tube 12, they assist in carrying torsional loads. The stiffness they provide are in the longitudinal direction to control the bending strength of the tube 12 and thereby control the critical speed of the shaft 10. It should also be understood that the fiberglass layer 16 assists in controlling bending and critical speed.

In production of a shaft 10 one merely advises the composite tube vendor of the internal and external diameter, the required critical speed, the torsional strength and fa- tigue resistance required for a specific applica tion, and the vendor varies the fiberglass layer 16, and the carbon graphite layer 18 to provide the desired results. The vendor is also advised of the total length that the tube is desired, from which the final desired length of the tube 12 will be cut by the manufacturer.

A particular application for a passenger car or light truck tube could be: tube length of 69.34 inches (1.76mm); tube internal dia meter 3.750 inches (95.25mm); tube external diameter 4.00 inches (101.6mm); with a critical speed of 6,000 r.p.m., torsional strength of 30,000 inch pounds (3.39 KN.m); and a fatigue strength (when assembled) of 75,000 cycles at a load of 1 2,000 inch pounds (1.36 KN.m). A shaft of such criteria would be required to bond length of 2.500 inches (63.5mm) to maintain a torsional lap shear stress at less than 500 pounds per square inch (3.45 MN5/m2) to provide an adequate safety factor when the shaft 10 is assembled in accordance with this invention.The actual length of the bond between the composite tube and the matching metallic member as required for a particular application can be calculated by using the following equation:

where L = bond length T = applied torque R = radius to center of bond line TAIIOW = allowable average torsional lap shear stress Referring to Fig. 2, the radially outer circumferential surface 20 of the attaching portion of the yoke 14 is tapered at a 1" angle such that the right end of the attaching portion of the yoke has a smaller diameter than the left end of the attaching portion thereof.

The axial length of this attaching tapered surface of this preferred embodiment is 2.500 inches (63.5mm) and this taper is applied to the yoke surface 20 as by grinding or turning during the machining thereof. The desirable range of the taper is 1" to 5-. In the preferred embodiment, a 1' taper is shown.

The inner surface 22 of the outer end 24 of the tube 12 is tapered at substantially a 1' angle in the matching direction as the taper on the outer surface 20 of the yoke 14 so as to be substantially parallel thereto.

The tube 12 is contemplated as having been cut off of a long composite tube (not shown) which is longer than the tube 12 and which can be utilized to cut off several tubes 12 to manufacture drive shafts 10. For example, since the tube 12 of this preferred embodiment is 69.34 inches (1.76mm), the long tube from which the tube 12 would be cut could be a multiple of this length, plus enough extra to accomodate material loss in cutting off the desired length from the long tube. It is also contemplated that if shafts of more than one length are being made, for example a shaft needing a tube of 69.34 inches (1.76mm) and a shaft of 40 inches (1 m), the longer tube could be the sum of these various lengths, plus enough material to accomodate cutting to length.This manner of manufacturing the tubes in long lengths and cutting to size reduces the cost of manufacturing each tube specially and separately to its final required size and also reduces the tube inventory requirements, since a specific length need not be cut until needed.

After the tube 12 has been cut to the desired length by any one of a number of well known methods of tube cutting, such as by a lathe or saw, the inner surface 22 of the outer end 24 (and the inner surface of the opposed outer end which may accomodate the metallic shaft member to be secured thereto) is machined as by grinding or turning to provide a 1 to 5 taper; however the particular taper chosen should preferrably be the same as the taper on the tube yoke. The length of this taper is also machined to be 2.500 inches (63.5mm).

After the tube yoke 14 and tube 12 have been machined with the desired taper, a special bonding material 26 is spread on the tapered outer surface 20 of the yoke 14, and the yoke surface is axially pressed into the tapered surface 22 of the tube 12, as hereinafter more fully described.

An adhesive which has been found to give satisfactory results is a two part epoxy structural adhesive available from the Hysol Division of The Dexter Corporation, Pittsburg, California and is identified by the number EA 9410.

This is a two part structural adhesive with a lap shear strength of 4500 p.s.i. (31 MN/m2) at 70oF (21 C) and can be cured at room or elevated temperature. The manufacturer recommends a bond line thickness from .001 to .010 inches (0.025 to 0.25 mm).

If the adhesive were mixed and merely used as supplied by the vendor, and the tapered shaft end 24 were pressed onto the tapered outer surface 20 of the yoke 14, there would be no control over the thickness of the adhesive. Thus, if too much axial pressure were applied the adhesive could be squeezed out excessively so that there would be direct nonbonding contact between the tube and the yoke. On the other hand, if during assembly, an insufficient axial load were applied, the bond line might be excessively thick, or not contacted by both the tube and the yoke, so that no or insufficient adhesion would take place between the tube and the yoke.

To avoid the above situations the bonding material, before applying, is mixed with high quality glass beads in proportion, by volume, of one part glass beads to ten parts adhesive, to provide a bonding material 26 suitable for this invention. The glass beads act like minature ball bearings during assembly, and spacers during curing.

The high quality glass beads can be purchased from the Johns-Manville Corporation, which has an office in Waterville, Ohio, under the designation &num;325 grade A glass beads.

These glass beads have great compressive strength and have an average nominal size of .003 inch (0.076mm) with a tolerance from the nominal size of plus .022 inches to minus .0005 inches (plus 0.051 to minus 0.01 3mm).

As seen in Fig. 2, the glass beads are mixed in the adhesive and a layer 26 of the mixed bonding material is applied to the tapered yoke surface 20. The layer 26 consists of glass beads 28 and adhesive 30. Since the glass beads 28 have a nominal average size of .003 inch (0.076mm) and a positive tolerance of .002 inches (0.051 mm), the applied thickness of the bonding material 26 should be slightly greater than .005 inches (0.1 27mm), thereby completely covering the largest diameter beads. If desired, the bonding material 26 can be applied to the tapered inner surface 22 of the tube 12, or to both tapered surfaces; however, in assembly this tends to force excess bonding material into the tube.It is more desirable to apply the bonding material to the outer surface 20 of the tube yoke, since in assembly excess bonding material will tend to be forced outwardly of the tube where it can be easily removed.

When assembling the tube yoke 14 into the outer end of the tube 24, substantial axial load is applied while at the same time the yoke and tube are twisted circumferentially slightly relative to each other to insure that direct bead contact is provided between the tube and the yoke tapers, and that no beads will be stacked upon one another. Since the beads are round, they will roll and attain a unilevel relationship when the axial and circumferential mounting motions are applied during assembly. This direct bead contact insures that a proper adhesive bond is present both along the length of the taper and circumferentially around the tapered surfaces. In some locations only the larger beads 28 will contact both members; in others, smaller sized beads will contact both members.However, because of the bead tolerances, the bond thickness specified by the adhesive manufacturer will be attained. It should be understood that simultaneously with bonding the tube yoke 14, a metallic drive shaft member can be simultaneously bonded to the opposite end of the tube 12. It should also be understood that metallic drive shaft end fitt ings other than tube yokes, such as stub shafts, can be assembled to the composite tube to form a drive shaft according to this invention.

The step of applying the bonding material 26 can be accomplished by any one of many well known methods of applying a controlled thickness layer of bonding material. It can even be applied as simply as using a spatula with a suitable thickness being applied until all of the beads are barely covered. However, for high volume production a more sophisticated method is preferably utilized. It should also be understood that inserting the end fitting into the composite tube encompasses placing the tapered end of the composite tube over the end fitting.

Claims

1. A method of attaching a resinous tubular member reinforced with fiberous material to a metal end fitting to form a drive shaft capable of transmitting torsional loads comprising the steps of a. providing a composite tube, b. cutting from said tube a sized composite tube having a length necessary to form said drive shaft, c. machining a conically shaped taper in the inner surface of at least one end of said sized composite tube, d. forming a metallic end fitting adapted to have one axial end thereof inserted into said tapered end of said sized composite tube, with said one end having a conically shaped taper thereon substantially corresponding in angle to the taper in said inner surface, e. preparing a bonding material including an adhesive and spacing members, f. applying said bonding material to at least one of said tapers, g. inserting said tapered end of said end fitting into the tapered end of said sized composite tube until said spacing members engage and space both said tapers to provide a controlled bond line, and h. curing said bonding material.

2. A method according to Claim 1 wherein said bonding material is applied to the conical taper of said metallic end fitting.

3. A method according to Claim 1 wherein the step of preparing said bonding material includes the step of mixing in said adhesive a plurality of substantially spherically shaped spacing members.

4. A method according to Claim 3 wherein the step of preparing said bonding material comprises mixing glass beads in an adhesive matrix.

5. A method according to Claim 1 wherein said step of preparing said bonding material comprises mixing glass beads having an average nominal size of .003 inches (0.076mm) with a tolerance of plus .002 inches to minus .0005 inches (plus 0.5mm to minus 0.013mm) in an adhesive matrix.

6. A method according to Claim 1 to 5 wherein the step of machining the tapers in the inner surface of said tube and on said one end of said end fitting comprise the steps of machining tapers in the range of 1' to 5'.

7. A method according to Claims 1, 2, 3, 4 or 5 wherein said step of inserting said tapered end of said end fitting is accompanied by circumferential rotation of said taper of said end fitting relative to said taper of said sized composite tube.

8. A method according to Claim 6 wherein the length of said tapers and the length of said bond line results in a torsional lap shear stress in bonding material which is less than 500 pounds per square inch (3.45 MN/m2).

9. A method as claimed in claim 1 and substantiallly as described herein.

10. A drive shaft when made by a method in accordance with any one of the preceding claims.