A FLEXIBLE DRIVE

Abstract: Vehicle driveline joints presently restrict shaft angularity, which results in lengthy driveshafts, whilst conventional flexible drives using links become too large in diameter when matching vehicle spring movements. The drive comprises hardened driving and driven flanges (1a, 1b), each with three, equally spaced, deep, radial grooves, facing one another, to entrap a concentric unit, consisting of three driving arms (3, 4, 5), journalled together at their centre, but each separately, rotatably mounted. Each arm has a roller (2) at its extremity running in a respective groove and is cranked such that one roller (2) engages driving flange (1a) whilst the other roller (2) engages identical driven flange (1b) but 180 degrees out of phase. Possible alternatives to rollers are balls, shoes, slippers or other suitable member. The arrangement permits drive to be transmitted between the flanges whilst the rotational axes are laterally displaced.

Description: A FLEXIBLE DRIVE The present invention relates to flexible drives. The drives may be used in road, off road, or rail vehicles or in industry. Restrictions on the angularity of Hooke joints and those of constant velocity with freedom for axial translation, cause driveshafts to be long in relation to the vertical movement of vehicles between their suspension bump and bounce stops, in addition to the continuous lesser movements made in traffic. Driveshaft length conflicts with competitive pressure to make improved use of the space occupied by the power unit, in order to maximise that available for passengers and goods. Flexible drives are not new and those which might have been expected to economise on the length occupied by driveshafts in recent automotive practice are not used, because when of suitable size and diameter for a road vehicle, they fall very short of the range of movement of a vehicle suspension. This largely results from their use of links to transmit torque between dancing rings and their driving and driven members, to reduce the friction, whilst simulating kinematically, the pairs of sliding surfaces, mutually at 90 degrees, of the intermediate member of the classic constant velocity Oldham coupling, acknowledged as the basis of the vast majority of such -2- couplings, though very many do not provide for constant velocity. Moreover, when this type of coupling is displaced from its central position, the intermediate member, or "dancing" ring, performs an orbital motion, twice per revolution, circular- or near circular, on a diameter equal to the displacement. This orbital motion results in an eccentric force derived from the centrifugal force of the "dancing" ring and partial weight of the drive links. Because of the limited primary suspension range of rail vehicles and their great weight, this eccentric force is usually acceptable, but becomes unacceptable given the spring range, suspension movement in traffic and relatively light weight of road vehicles. A more recent type to appear in rail traction, providing constant velocity, utilises three concentric driving arms journalled together and connected by links to simulate a heavy floating member, whilst driving, driven and floating members lie in one plane. When the suspension is displaced, the assembly of driving arms, journalled together as a floating member do not have any orbital motion and continue to run stably, but at a deflection of one half that of the suspension, with the driving arms continuously making rotational adjustments relative to each other whilst ever the displacement persists. However with six links spaced around the periphery, the vertical range of the flexible drive is restricted by the clearance between the ends of the links before they foul one another, whilst the resulting large journal diameters of the concentric assembly encourages the use of plain bearings, rather then anti-friction types, that is ball, roller, or needle, at the centre of the driving arms forming the floating assembly, where the reaction load due to each pair of driving links, becomes twice that in the links themselves. For these reasons vertical movement is restricted, despite the large diameter, whilst frictional losses are inevitably larger than those normally anticipated. According to the present invention, there is provided a flexible drive comprising a driving flange, a driven flange facing the driving flange, characterised by guides disposed in each flange and extending radially with respect to the centre of the flange, members retained for movement in the guides and means for operatively connecting the members in the two flanges together whereby torque may be transmitted through the members between the flanges and the rotational axis of the flanges moved laterally relative to one another. In a preferred embodiment of the invention torque is transmitted by means of lipped, guided, or spherical rollers, themselves journalled on anti-friction bearings, engaging with and constrained by, the radial slots, equally spaced in the driving and driven flanges. The rollers are carried in pairs on the driving arms, at least and preferably three, although more than three, might be used for very powerful heavy vehicles. The assembly of driving arms is located between the driving and driven flanges and concentrically journalled together at their centres on anti-friction bearings, whilst each arm carries a pair of rollers, one engaging the driving flange and accepting driving torque, whilst the other, at the opposite end of the arm, engages the radial slot of the opposing driven flange to transmit its share of the driving torque. The roller lips, or their spherical profiles locate and maintain the parallelism and axial relationship of driving and driven flanges. To allow for small versine movements, as the vehicle rises and falls on a typical suspension controlled by radius links using rubber bush fulcrums, such as are employed to locate a MacPherson strut front suspension and for wear in these features, both of which result in small axial misalignments and changes in length, rubber bushes are located in the driving and driven flanges, but also transmitting driving torque, through shouldered, cantilevered, inner bushes, in a well known way. Though fairly stiff radially and in resistance to misalignment, the rubber bushes are relatively soft axially, to give the whole drive assembly a low longitudinal resilience, to minimise end loading during the small extensions and contractions required by the suspension. In action, the geometry of employing three, or more, separately journalled, concentric, driving arms, fitting inside one another, ensures there is no radial, or eccentric force, since there is no orbital motion of the floating assembly of driving arms and under sustained deflection of the suspension, the group of concentric driving arms continues to run stably. Moreover the group only reflects one half of the overall movement of the suspension due to the geometry of using separate driving arms, journalled together in conjunction with rollers free to adjust radially in the driving and driven flange guides, or slots. As a consequence of separating driving and driven flanges and using rollers in place of links, the peripheral dimension is reduced to a minimum and therefore the diameter of flexible drive to transmit a given torque, whilst providing for a given suspension displacement, before the three driving, or the three driven arms clash with one another, is likewise reduced to a minimum. The provision for misalignment and axial freedom or resilience of conventional flexible drives, normally lies in the bushes in the driving links, where the use of spherical rubber types is common, even though the rubber characteristics of the bushes places a further limitation on the angling of the links, whilst the links themselves are made still shorter by reason of the large diameter of spherical rubber bushes so that the risk of the links clashing with one another under severe deflections, or of torsionally overloading the bushes as the links angle, compromise and conflict with the need for a substantial range of movement to match the suspension requirements of road and off highway vehicles. Herein provision for axial misalignment and low axial resilience, is also provided by rubber bushes, but they have no influence on the working range of the flexible drive. The rubber bushes are fitted between the radial slots, on the blind side, as it were, of the driving and driven flanges. Bush radial stiffness is moderately high, i.e. in the direction in which it receives driving torque and accepts the weight of the drive unit, whilst their proportions also ensure relatively low resistance to axial misalignment and provide for low longitudinal, or axial resilience. The bushes thus cater for these needs without restricting the working range of the suspension, which is determined by fitting stops to just prevent the rollers, in either driving, or driven flanges, from touching at the inner end of each pair of radial slots, as they pass through a symmetrical position on either side of the centreline at full deflection. Whilst this substantially increased range of displacement is gained by allowing for greater angular variation between the driving arms, this is offset by the compact size of the unit described with its smaller size, weight, and therefore, angular inertia of each driving arm and roller pair, in relation to that of adjacent parts. Again and more importantly, during one revolution, or during a part of a revolution, the net variation of driving torque equates to zero, as the small angular accelerations of each driving arm under sustained suspension deflection cancel one another out. A further feature favouring separation of driving and driven rollers and guides to their respective driving flanges, derives from the primary reaction loads at the centre of the concentric group of driving arms resulting from driving and driven loads at rollers and guides. The three primary reaction loads due to the driving arms at their centres, occur in the vertical plane, symmetrically and at the centre of the drive unit to balance one another out. There are secondary torques within the driving arms due to their cranking and whilst the arms are stressed and proportioned to match them, these torques are symmetrical, equal and opposite in each arm and are internal forces without external reaction. A second embodiment of the invention uses the same spherical, lipped, or guided rollers, mounted in pairs at right angles to one another, on a star shaped "dancing" member to simulate the constant velocity action of the classic Oldham coupling, by engaging guideways, similarly at right angles to each other, in driving and driven flanges. Using rollers on anti-friction bearings avoids the sliding friction which handicaps this type of flexible drive. Further the centre driving element employing rollers is lighter than sliding types, which minimises the eccentric force, derived from the centrifugal force of the "dancing" centre element, during displacement of the suspension, or off centre running, when it orbits twice per revolution of the drive, on a diameter equal to the deflection of the suspension. Even so this embodiment is recommended for low cost arising from its simplicity, rather than for high speeds, since at high revolutions there can still be a considerable eccentric force when large deflections occur. For minor axial misalignment combined with low axial resilience, rubber bushes favouring these features are fitted at the driving and driven flanges, where their firm radial stiffness serves to support the weight of the coupling and cushion driving torque. The second embodiment is seen as suitable for medium and slow speed vehicles, some rail applications and for industrial use such as arises with adaptations needed for machine tools, etc. An alternative, or inversion of the second embodiment occurs from exchanging rollers and guideways, between flanges and yoke. Thus a line of rollers mounted on anti-friction bearings, .typically seven in number, are fitted to seven pins projecting from each of the driving and driven flanges across a diameter, equally pitched and facing one another, to be engaged by the "dancing" member replacing the driving yoke, which then consists of two short guideways, facing outwards, mutually at right angles and each long enough to span a little more than two roller pitches. Other features remain the same. Other embodiments of the invention are described below. Embodiments of the invention will now be described by way of example with refercr-..,. to the accompanying drawings in which:- Figure la shows a side elevational view in section of a first form of drive according to the invention, Figure lb shows an end view in section of the drive of Figure la taken along the line A-A, Figure 2 diagrammatically illustrates the positions that parts of the drive of Figure la and lb adopt in various deflected positions. Figure 3 diagrammatically illustrates the application of the invention to a front wheel drive car, Figure 4a shows a side elevational view in section of a second form of drive according to the invention. Figure 4b shows an end view in section of the drive of Figure 4a taken along the line A-A, Figures 5a, 5b, 5c and 5d diagrammatically show the drive of Figure 4a and 4b in a deflected condition, Figure 6 shows a sectional side elevation of another embodiment, Figure 7 illustrates the embodiment of Figure 6 in end view, Figure 8 depicts the typical envelopes of an automotive driveshaft and that of the invention for the same spring deflection, at A and B respectively. Figure 9 is a sectional side elevation of the embodiment of Figures 6 and 7 used with front wheel drive. Figure 10 is a semi-diagrammatic end view showing how the arrangement of Figures 6 and 7 simplifies automotive applications of four wheel drive. Figure 11 depicts a sectional side elevation of a further embodiment, Figure 12 shows an end view of the embodiment of Figure 11, and Figure 13 shows the embodiment applied to a front wheel drive vehicle in sectional side elevation, and Referring to Figures la and lb, the drive comprises identical driving and driven flanges la and lb arranged facing one another, each having three, hard surfaced, radial guides, spaced 120 degrees apart and with lips, or radiused, to accept lipped, plain, or spherical rollers 2. Identical radial guides in driving and driven flanges la and lb are assembled 60 degrees out of phase with one another, so that each radial slot in the driving flange la, matches one in the driven flange lb, but is on the opposite side of the centreline, that is 180 degrees out of phase. Figure 2 depicts this diagrammatically. the radial guides in the driving flange are referenced 11, 12 and 13 in Figure lb. Driving arms 3,4 and 5 are journalled together concentrically, at their centres and each ana has a roller at its extremity and is cranked, such that one roller engages driving flange la whilst the other roller engages identical driven flange lb, but 180 degrees out of phase. Arm 3 is manufactured integrally, whilst arms 4 and 5 are typically made in two parts, held by screws and spigoted and keyed together. Arm 3 is depicted with its centre bearing 3a using roller bearings 3b without their inner or outer rings and with side washers 3c of low friction material to position the bearings, whilst the smaller-diameter and greater length between driving arms 4 and 5 suggest the use of needle bearings which are depicted caged and in their own housing. The journal surfaces of driving arms 3, 4 and 5 are suitably hard for use with roller needle or ball bearings. The cranked driving journals of driving arms 3,4 and 5 are also suitably hard for employment with roller or needle bearings. The driving arms 3, 4 and 5 are located axially and retained by lips machined typically inside their rollers, a shoulder machined at the inner end of the cranked arms, together with a low friction washer and circlip at the extreme ends. These axial location arrangements of the driving arms 3, 4 and 5 complement the requirements of axial location of the driving and driven flanges la and lb, which are .by means of the lips on either side of the rollers 2, as a result of their radius if spherical, or from the sides of the guideways and the ends of plain rollers. Clearances are illustrated between the side cheeks of driving arms 3,4 and 5, to avoid interfering with these low friction arrangements, whilst low friction washers 7 are used between the cheeks of driving arms 3 and 4 to position the roller bearings. Driving and driven flanges la and lb typically receive and transmit torque from driveshaft 6, by means of spigoted and cantilevered bushes 8, whilst a central bolt 14, both tightens them in position and secures them through the centre of a rubber bush, or block 9, whose outer case is located in driving and driven flanges 1 and retained by a circlip, or similar means. The rubber element of the bushes 9 is typically proportioned and preloaded radially during manufacture to provide a low axial stiffness, allow for small axial misalignment with suspension deflection, whilst presenting a moderately high radial stiffness to carry the weight of the coupling and transmit driving torque. To contain grease lubrication, typically, a thin plate 10 is secured under nuts 15 of the through bolts 14 securing spigots 8 and bushes 9 and sealed by adhesive to the flange 17 of driveshaft 6. The plate 10 approaches close to the outer rings of driving and driven flanges la and lb, does not touch them and approximately matches the end of the rims of flanges la and lb so that a reinforced rubber sealing bellows 18 can be sprung into place and separately clipped and adhered to plate 10 and flanges la and lb. Alternatively, though not illustrated, the whole assembly, from gearbox, or differential end, to the driveshaft 6 used for output, can be contained in a casing bolted to the gearbox end, split and bolted horizontally at its centre, profiled towards the driven end to match the vertical movements of the suspension, with the output end oval shaped and provided with an aperture only large enough to cater for the vertical movement of the housing containing the centre bearing of the yoke from the MacPherson strut which supports driveshaft 6 and half the weight of the flexible drive. Thus the oval shaped end aperture of the casing forms a shallow weir for lubricant which is a starting point in their containment since the weir height is above the filling level and below that of the stationary, vertical reinforced rubber seal, with oval bellows arranged to accept suspension movement and clipped at its centre to an extension of the circular housing of the centre bearing of the yoke attached to the MacPherson strut and supporting the driveshaft 6 and half of the weight of the flexible drive unit. The outer edges of this .stationary seal are bolted and sealed to the casing. In this latter way oil lubrication can be used. Figure 2 diagrammatically illustrates the relative displacement of the driver and driving flanges and the corresponding position of the driver and driving balls for various rotational positions. As can be seen the displacement of the driving arms 3,4 and 5 is half that of the flange displacement. Referring to Figures 4a and 4b, driving and driven flanges 41a and 41b again face each other and are equipped with hard surfaced guides for rollers 42 at right angles to each other. Typically two, or four spigoted rubber bushes 44, in each driving and driven flange 41a and 41b, provide for the same functions as described for the first embodiment. Two pairs of rollers 42, mounted on anti-friction bearings from the two pairs of arms of yoke 43, again at right angles to one another, engage in the guideways 45 of driving and driven flanges 41a and 41b. The lips 46 of the guideways 45 locate the driving yoke 43 and driving and driven flanges 41a and 41b endways, whilst the guideways, rollers 42 and yoke 43 transmit torque. The rollers 42, their bearings and the arms of yoke 43 are used for end location in the same way as for the first embodiment. Containment of grease lubrication is carried out in the same way as for the first embodiment, or arranged with a bolted casing and stationary end seal for oil lubrication. In use of the drives on, for example, a front wheel drive automobile, vertical movement of the steered wheels relative to the gearbox (not shown) is accommodated by relative movement of the driven and driving flanges as shown diagrammatically in Figures 5a to 5d. Axial movement of the steered wheels relative to the transmission is accommodated by a sliding joint on the inner driveshaft as shown diagrammatically in Figure 3. In Figure 3 the position of the steered wheels W and of the transmission T at the extremes of their movement is shown in dash dotted outline. Figures 5b and 5d diagrammatically show sections through the drive with the driven flange F in its uppermost position and lowermost position relative to the driving flange F'. Figures 5a and 5c diagrammatically show end views of the drive corresponding to figures 5b and 5d. Referring to Figure 6, the arrangement comprises, identical, hardened, driving and driven flanges 61a and 61b, each having three deep radial grooves on the surfaces facing one another, spaced 120 degrees apart, radiused to match six large hardened balls 62, housed in deep spherical seats in three, concentrically journalled, driving arms 63, 64 and 65. Each driving arm has one ball registering in the driving flange and at the opposite end, one registering in the driven flange. Driving arms 63 and 64 have a set towards the centre and their journals fit one inside the other, whilst driving arm 65, the inner one, journalled inside 63 and 64, is divided into two parts, for assembly purposes and keyed, or splined together, though the connection is not illustrated. The journals of each driving arm are carried from one another by needle bearings, not illustrated, allowing the arms to make small torsional movements independently, but still forming one concentric unit. Through the centre of this concentric unit and again journalled on needle bearings, a long pin 66, applies preload at each end to the rear surfaces of the driving and driven flanges 61a and 61b, using a two or three part collect 67, illustrated, or screw threads and locknuts, not illustrated, or other means. Rubber washers 68 assist distribution of the preload equally to three pronged spring steel plates 69, figure 2, having ball bearings 70, trapped in spherical depressions, or cages, at their extremities. In figures 6 and 7, grooves 71 in the driving and driven flanges 61a and 61b, but spaced at 180 degrees to one another, locate one of the three prongs in each spring steel plate 69. From the construction described the preload maintains driving and driven flanges 61a and 61b, parallel to each other at all times, still leaving the need to cater for the small angularities, customary with front and rear wheel suspensions in automotive practice, even through the arrangement already caters for the full vertical rise and fall of the suspension. There is also the need to cater for the small alignment discrepancies found in industrial plant. Three rubber bushes 72, equally spaced between the deep radial grooves of driving and driven flanges 61a and 61b, as shown in figures 6 and 7, are engaged by means of cantilevered driving bushes 73, spigotted into the three integral driving arms of driving and driven shafts 74a and 74b and tightened in position by through bolts 75, in a well known manner. Figure 2 already described illustrates how the centre of the three concentric arms, moves up or down by only one half of the deflection between driving and driven flanges. Figure 8 at A, shows the space envelope typical to automotive driveshafts with rise and fall of the springs and at B, the very much shorter length, but larger diameter, needed by the arrangement according to the invention to cater for the same movements. Figure 9 illustrates application of the arrangement, of Figures 6 and 7 to a front wheel drive vehicle and also shows how the increase in diameter, shown at B in figure 8, fits within the ground clearance of other essential front wheel drive features such as the differential and the lower suspension swivel pin of a MacPherson strut type of suspension. The vertical displacement, indicated in chain dot, is illustrated as though the chassis moved up and down by the total amount of the spring deflection. Figure 10 in semi diagrammatic form, illustrates the application of the arrangement of Figures 6 and 7 to one side of a powerful sports car, or limousine, with conventional engine layout, so as to facilitate application of four wheel drive, without need to raise the engine, place it off centre, unduly lengthen the chassis to allow fitting driveshafts at an angle to the longitudinal centre line, or fit additional transfer gearboxes to centralise location of the differential. On the opposite side there is ample space for the sort of constant velocity driveshafts currently in use. A further embodiment of the invention is depicted in Figures 11 and 12, in which identical, hardened driving and driven flanges 81a and 81b are arranged to face one another. Each flange has a deep groove, pierced by a smooth slot, extending across the full face width, passing through the flange centres, radiused to accept large, hardened, driving balls 82 and with the deep grooved slots at 90 degrees to each other. The four large driving balls are housed in a cage 83, allowing two of the balls to run in each of the slots, mutually at right angles to one another so as to match, but with low friction, the method of Oldham couplings and their numerous industrial derivatives using links and "floating" rings. Thus whenever the driving, or driven flanges are displaced, as in Figure 5, the cage 83 performs an orbital motion, of amplitude equal to the deflection and of frequency equal to twice the revolutions of the driving flange, with the balls enabling free movement of the cage, whilst transmitting the driving torque. To ensure proper contact of the balls, even under sudden and overload conditions, in the same way as for the embodiment of Figures 6 and 7, the smooth rear surfaces of the hardened driving and driven flanges 81a and 81b react the preload by means of ball bearings 84, housed in spherical depressions at the ends of spring steel plates 85. The preload is applied by spring plate 85, rubber springs or belleville washers 86 and maintained by the rivets 87, or other means of fastening. The sides of cage 83, which penetrate the driving and driven flanges 81a and 81b, are proportioned, or dimensioned, so that the large driving balls 82, the radius of the deep grooves and the preload, at full driving and overload torque, in combination ensure there is no contact between the sides of the grooves and the cage 83 and that the balls are never unseated or suffer from loss or contact. -21- The opposing faces of driving and driven flanges 81a and 81b are held parallel to one another by means of the driving balls 82 and the preload, as in the preferred embodiment. Four rubber bushes in the driving and driven flanges 81a and 8lb and their spigoted and cantilevered hollow driving bushes mounted in driving and driven shafts 88, in a well known way, as in the first embodiment, provide for small angular misalignments. Whenever the centrelines of driving and driven flanges 81a and 81b are displaced an eccentric force arises, varying at each point of the orbital path described by cage 83 and derived from the centrifugal force due to the combined weight of cage 83, hardened steel balls 82 and the preload system, comprising ballbearings 84, spring steel plates 85 and rubber springs, or belleville washers 86. These together weigh much less than the "floating" rings and links of other flexible drives providing a constant angular velocity, so that advantage can be taken of the increased deflection of this embodiment of the invention, compared to other such drives, to operate across greater deflections of the driving and driven flanges. Whilst simpler than the embodiment of Figure 6 and 7 and able to match the same deflections and spring movements, because of the eccentric force at high deflections, it is not as suitable for high rotational speeds as the embodiment of Figures 6 and 7. Figure 10 illustrates application of the second embodiment to a motor vehicle with front wheel drive. The balls or rollers running in the guides of the above described embodiments could be replaced by shoes or slippers appropriately shaped and dimensioned running in appropriately shaped and dimensioned slots. It will be appreciated that the above embodiments has been described by way of example only and that many variations are possible without departing from the scope of the invention.

Claims: CLAIMS 1. A flexible drive comprising a driving flange (la) , a driven flange (lb) facing the driving flange, characterised by guides (11,12,13) disposed in each flange and extending radially with respect to the centre of the flange, members (2) retained for movement in the guides and means for operatively connecting the members (2) in the two flanges together whereby torque may be transmi ted through the members (2) between the flanges and the rotational axis of the flanges moved laterally relative to one another. 2. A flexible drive as claimed in claim 1, in which the members (2) comprises balls. 3. A flexible drive as claimed in claim 1, in which the members (2) comprise slippers or shoes. 4. A flexible drive as claimed in claim 1, in which the members (2) comprises rollers. 5. A flexible drive as claimed in claim 3 or 4, in which the members (2) engage with and are contained by the guide. 6. A flexible drive as claimed in claim 4, or claim 5 when appendant to claim 4, in which the rollers are journalled on anti-friction bearings. 7. A flexible drive as claimed in any preceding claim, in which the means for operatively connecting the members (2) together comprise three driving arms (3,4,5) . 8. A flexible drive as claimed in claim 7, in which the three driving arms (3,4,5) are equidistantly spaced. 9. A flexible drive as claimed in claim 7 or 8, in which the arms are concentrically journalled together at their centres on anti-friction bearings (3a,3b) . 10. A flexible drive as claimed in claim 4, in which the rollers (2) are lipped and located in the guides to maintain the parallelism and axial relationship of driving and driven flanges (la,lb) .

Inventors: DOWLING JOHN, DOWLING, JOHN
Applicants: COBIC DOWLING TECH LTD, COBIC DOWLING TECHNOLOGY LIMITED
Application year: 1992
Main classification: F16H21
IPC codes: B60K17, F16D3