GB2566528A

GB2566528A - Infinitely variable multi-epicyclic friction transmission system for electric motor

Info

Publication number: GB2566528A
Application number: GB1714994.9A
Authority: GB
Inventors: Mcanulla Aidan
Original assignee: Individual
Current assignee: Individual
Priority date: 2017-09-18
Filing date: 2017-09-18
Publication date: 2019-03-20
Also published as: GB2567745A; GB2567745B; GB201714994D0; GB201815192D0

Abstract

An infinitely variable multi-epicyclic friction transmission, for an electric motor in an electric vehicle, comprises a plurality of twin planetary cone assemblies disposed parallel to a main shaft (1, fig 3) and having a torque tube 17 constituting a common outer planet attached to a planetary cone 22, wherein the slant height of the cone 22 is parallel to the main shaft (1). A plurality of planetary shafts 18 are disposed adjacent and parallel to the torque tube 17 and bear a series of slidable apertured ellipsoid planets 19 which are situated between a series of inverted vee-rings 6 that are compressed towards each other thus forcing ellipsoid planets 19 radially outwards into contact with the torque tube 17. Each planet 19 and vee-ring 6 forms a separate epicyclic gear train. A reaction ring 25 is disposed around each planetary cone 22 and is configured to slide along the planetary cone 22 to vary a gear ratio. The vee-rings 6 are mounted on an outer circumferential surface of a drum (3) and a spacer ring limits radial movement of the planets 19 past the torque tube 17.

Description

The present invention relates to electric motors, and in particular to an infinitely variable transmission system for electric motors.

Background Of The Invention

An electric vehicle (EV), also referred to as an electric drive vehicle, uses one or more electric motors or traction motors for propulsion. An electric vehicle may be powered through a collector system by electricity from off-vehicle sources, or may be self-contained with a battery or generator to convert fuel to electricity. EVs include road and rail vehicles, surface and underwater vessels, electric aircraft and electric spacecraft.

In the context of electric road vehicles, at present Tange anxiety’ is not a problem for city driving with a short commute to work and leisure activities. However, 'range anxiety' occurs for long journeys over 100 kilometres.

Continuously variable transmission (CVT), also known as a single-speed transmission, stepless transmission, pulley transmission, or, in case of motorcycles, a twist-and-go, is an automatic transmission that can change seamlessly through a continuous range of effective gear ratios. This contrasts with other mechanical transmissions that offer a fixed number of gear ratios. The flexibility of a CVT allows the input shaft to maintain a constant angular velocity. A belt-driven design offers approximately 88% efficiency, which, while lower than that of a manual transmission, can be offset by lower production costs and by enabling the engine to run at its most efficient speed for a range of output speeds. When power is more important than economy, the ratio of the CVT can be changed to allow the engine to turn at the RPM at which it produces greatest power. This is typically higher than the RPM that achieves peak efficiency. In low-mass low-torque applications a belt driven CVT also offers ease of use and mechanical simplicity. Steel belt driven CVTs are now the dominant variable transmission used in cars.

Epicyclic gearing or planetary gearing is a gear system comprising one or more outer gears, or planet gears, revolving about a naseral, or sun gear. Typically, the naser gears are mounted on a movable arm or carrier which itself may rotate relative to the sun gear. Epicyclic gearing systems also comprise an outer ring gear or annulus, which meshes with the planet gears. Planetary gears, or epicyclic gears, are typically classified as simple or compound planetary gears. Simple planetary gears have one sun, one ring, one carrier, and one planet set. Compound planetary gears may comprise one or more of the following three types of structures: meshed-planet - there are at least two more planets in mesh with each other in each planet train, stepped-planet - there exists a shaft connection between two planets in each planet train, and multi-stage structures - the system contains two or more planet sets. Compared to simple planetary gears, compound planetary gears have the advantages of larger reduction ratio, higher torque-to-weight ratio, and more flexible configurations.

Epicyclic gearing with toothed gear wheels is very common in automatic gear boxes. A friction drive or friction engine is a type of transmission that, instead of a chain and sprockets, uses two wheels in the transmission to transfer power to the driving wheels. The problem with this type of drive system is that it is not very efficient. Trying to duplicate epicyclic gearing with friction drives is very difficult because if the planets are mounted on fixed stubs and at fixed distances from each other, they cannot be forced against other components to give a friction drive.

A cone CVT varies the effective gear ratio using one or more conical rollers. The simplest type of cone CVT, a single-cone CVT, uses a wheel that moves along the slope of the cone, creating the variation between the narrow and wide diameters of the cone. In a planetary CVT, the gear ratio is shifted by tilting the axes of spheres in a continuous fashion, to provide different contact radii, which in turn drive input and output discs. The system can have multiple planets to transfer torque through multiple fluid patches.

In view of the above, there is a need to provide an improved transmission system for electric motors.

Summary

According to the present disclosure there is provided a transmission system as detailed in claim 1. Advantageous features are recited in dependent claims.

The present disclosure provides a mechanism for increasing the torque capacity of an infinitely variable transmission system which relies solely on rolling friction. This is accomplished by having a stack of epicyclic friction gears in series.

The transmission system of the present disclosure may be configured to have sufficient torque at its output to drive the road wheels of a motor vehicle. The greatly enhanced output of torque that the system produces is by means of its multi-epicyclics stacked in series. These work in an analogous way to a multiplate clutch where friction discs are compressed in series to transmit much more torque by static friction than by one disc alone.

Brief Description Of The Drawings

The present application will now be described with reference to the accompanying drawings in which:

Figure 1a illustrates a cylindrical drum according to an embodiment of the present disclosure;

Figure 1b illustrates a main shaft according to an embodiment of the present disclosure;

Figure 2 illustrates an internally splined driver for insertion in the cylindrical drum of Figure 1a, according to an embodiment of the present disclosure;

Figures 3 and 4 illustrate a structure in which a series of vee-rings and intermediate ellipsoid planets are located about a main shaft;

Figures 4a and 4b show a pressuriser ring according to an embodiment of the present disclosure;

Figure 5a illustrates a half planet carrier/rotor combination, according to an embodiment of the present disclosure;

Figure 5b illustrates twin planetary cone assemblies comprising first and second planetary cone assemblies, according to embodiments of the present disclosure;

Figure 6 illustrates an end view of the transmision mechanism, according to an embodiment of the present disclosure;

Figure 7 is a perspective view of an outer casing for the transmission system, according to an embodiment of the present disclosure;

Figure 8 illustrates stator or reaction rings, according to an embodiment of the present disclosure;

Figure 9 is an end view of electric motors on the outer casing for controlling the spacing of the reaction rings and consequently the gear ratio, according to an embodiment of the present disclosure;

Figure 10 illustrates an infinitely variable transmission system according to an embodiment of the present disclosure;

Figure 11 illustrates the infinitely variable transmission system of Figure 10, showing the same components but with one extra component, namely an idler planet, according to an embodiment of the present disclosure;

Figure 12 shows a complete twin cone planet assembly comprising two cones, one torque tube, two shafts of ellipsoids, two spacer rings, and two bearing/mounts, according to an embodiment of the present disclosure;

Figure 13 is a perspective view of a complete twin cone planet assembly according to an embodiment of the present disclosure;

Figure 14 shows a ring ensemble of rings, the innermost cam rings with an incline on one side rotate en bloc with the rest of the vee rings; the outermost cam rings are bolted to the drum; according to an embodiment of the present disclosure;

Figure 15 illustrates a half planet carrier/rotor combination, according to an embodiment of the present disclosure; and

Figures 16a to 16e illustrates various embodiments of the vee rings used in Figure 14, according to embodiments of the present disclosure.

Detailed Description Of The Drawings

The present disclosure provides an infinitely variable transmission system for an electric motor. The infinitely variable transmission system according to the present disclosure comprises a planetary cone transmission system, but unlike most planetary transmissions it has no toothed gear wheels whatsoever. The transmission system according to the present disclosure can therefore be classified as a friction gearing system. The driving force is produced by rolling friction only. Friction gearing is seldom used as it is incapapable of transmitting much power. An example where rolling friction will transmit considerable power is a railway locomotive.

The transmission system according to the present disclosure may be used for a range of electric motors. An axial flux motor whose topology comprises a central stator and twin external rotors is particularly suitable for the transmission system according to the present disclosure.

Accordingly, the present disclosure provides an infinitely variable multi-epicyclic friction transmission system for an electric motor, the system comprising: a main shaft; a plurality of twin planetary cone assemblies disposed parallel to the main shaft, each planetary cone assembly comprising: a torque tube constituting a common outer planet attached to a planetary cone at either end, wherein the slant height of the cone is parallel to the main shaft; a plurality of planetary shafts disposed adjacent and parallel to the torque tube, each planetary shaft configured to bear a series of slidable apertured ellipsoid planets, a spacer ring provided at each distal end of the torque tube to limit radial movement of the ellipsoid planets beyond the torque tube; a drum 5 disposed between and parallel to the planetary cone assemblies, the drum configured to bear a series of inverted vee-rings on an outer circumferential surface of the drum, wherein the vee-rings are configured to slide along the drum; wherein the apertured ellipsoid planets are configured to alternate with the series of inverted vee-rings, each vee-ring and each ellipsoid planet constituting a separate epicyclic gear train, the vee-ring being the sun gear and the ellipsoid planet being the inner planet, wherein the vee-rings are configured to be compressed together thus forcing the ellipsoid planets radially outwards; and further comprising a reaction ring disposed around each planetary cone and configured to slide along the planetary cone to vary a gear ratio.

The basic principle of the system is to force the twin planetary cone assemblies onto the reaction rings with as great a force as possible. When multi-epicyclics are connected in series the original force is transmitted to the next member and so on.

The system of the present disclosure may be configured to have sufficient power at its output to drive the road wheels of a motor vehicle. The greatly enhanced torque output that the system produces is by means of multiepicyclics stacked in series. This is analogous to a multiplate clutch where friction discs are compressed in series to transmit much more torque by static friction than by one disc alone.

In the system described herein where rolling friction is involved there are a series of inverted vee-rings alternating with a series of ellipsoidal planets therebetween. Each vee-ring and each ellipsoid planet together constitute a separate epicyclic gear train; the vee-ring being the sun gear, the ellipsoid planet the inner planet and the torque tube their common outer planet. Hence the term multi-epicyclic used the description. The vee-rings and the intermediate ellipsoid planets are configured to be compressed and the ellipsoid planets forced out radially.

The system described has a plurality of twin planetary cone assemblies. Between three and six such assemblies may be employed. It has been determined through experimentation that six such assemblies is the maximum that can advantageously be used. Using six assembles may not transmit more power but due to the very high forces involved the load may be distributed over a greater number of components. The twin planetary cone assemblies may be mounted in a planet carrier. The twin planetary cone assemblies may be configured to move out radially away from the main axis in slots in the planet carrier. The term “twin planetary cone assembly” denotes that the assembly has twin cones, or a pair or cones, one on each end of a torque tube. Each twin planetary cone assembly may comprise two largely hollow cones attached to a torque tube, along with a plurality of planetary shafts for bearing ellipsoid planets, two spacer rings and two bearings/mounts, as illustrated in Figure 13. The two cones, one at each end of the torque tube may be configured to transmit power at a fixed angle unlike a constant velocity joint in a car where the angle can vary. The reason for the fixed angle is to keep the slant height of the cone parallel to the main axis. By keeping the slant height of the cone parallel to the main axis, the one or more reaction rings can slide easily along the cones to vary the gear ratio.

The vee-rings and the intermediate ellipsoid planets are configured to be compressed and the ellipsoid planets forced out radially. Such compression may be effected in a number of ways. Figures 1 and 2 illustrate an example of a configuration for achieving such compression, according to an embodiment of the present disclosure.

Figures 5 and 15 illustrates components of an axial flux electric motor. The axial flux motor may be a brushless, synchronous three-phase motor. Refering to Figure 1a, a splined cylindrical drum 3 which constitutes the stator of the electric motor, defines a cavity therethrough. Two holed discs are disposed internally towards the centre of the drum 3 and are integral with the drum 3, as shown by the dotted lines in Figure 1a. Slots 3a are defined in two opposite sides of a centre of the drum 3. Referring to Figure 2, an internally splined driver 2 is configured to be disposed in a centre portion of the drum 3. The internally splined driver 2 is configured to be attached to a main shaft 1 as illustrated in Figure 1b. The driver 2 is thus configured to rotate with the main shaft 1. The main shaft 1 may be threaded through the splined driver 2. The driver 2 may be in the shape of an elongated rhombus or diamond shape. When disposed in the centre of the drum 3 and on the main shaft 1, ends of the driver 2 may protrude through the slotd 3a. It will be seen in Figure 1a that there is ample space on each side of the drum 3 to accommodate an electric motor. This is a major feature of the system in that space is saved by having the motor inside the transmission. A conventional cylindrical motor may be used but an axial flux motor is especially suited. A central stator (half on one side and half on the other) and twin permanent magnet rotors is ideal. Referring to Figure 1, inverted vee-rings 6 are configured to slide longitudinally along an outer cirumference of the drum 3.

Figures 3 and 4 illustrate a structure in which a series of vee-rings 6 and intermediate ellipsoid planets 19 are arranged about the main shaft 1. Figure 3 is a perspective view illustrating the series of vee-rings 6 arranged about the main shaft 1 with the splined driver 2 at a centre of the series of vee-rings 6. Figure 4 is a view illustrating a plurality of planetary shafts 18 configured to bear a series of intermediate ellipsoid planets 19, according to an embodiment of the present disclosure. End rings 8 may be provided at outer extremeties of the series of vee-rings 6. That is, an end ring 8 may be disposed at each of distal ends of the cylindrical drum 3. The end rings 8 may be configured to have an incline on their inner side only. The vee-rings 6 may be pressurised from the centre of the cylindrical drum 3 towards the distal ends thereof, as explained below.

Figure 4 is a cross-sectional view of the structure of Figure 3, according to an embodiment of the present disclosure. Referring to Figure 4, when a pressuriser ring 4, with ball bearings 5 each side, is slid onto the centre of the cylindrical 8 drum 3 it engages with the splined driver 2 which is fixedly attached to the main shaft 1. A cam ring 7 is disposed on the splined drum 3 and adjacent to each side of the pressuriser ring 4. If the main shaft 1 is rotated in one direction and then the other direction the splined driver 2 and pressuriser ring 4 will move several degrees each way. The movement of the splined driver 2 and pressuriser ring 4 is limited by the width of the slots 3a in the drum 3. The ball bearings 5 roll on the cam rings 7 forcing them out sideways or in a longitudinal axis direction. Thus, when the main shaft 1 is rotated, the bearings 5 roll on the inclines of the cam rings 7 forcing the cam rings 7 to move longitudinally along the drum 3 and compress the vee-rings 6, forcing the ellipsoid planets 19 radially outwards. This is illustrated in Figure 4d especially. Refering to Figure 4d, each planetary cone assembly comprises a torque tube 17 constituting a common outer planet attached to a planetary cone 22 at either end thereof. The slant height of the planetary cone 22 is parallel to the main shaft 1. The planetary shaft 18 is disposed adjacent and parallel to the torque tube 17. The planetary shaft 18 is configured to bear the series of slidable apertured ellipsoid planets 19. A reaction ring 25 is disposed around each planetary cone 22 and configured to slide along the planetary cone 22 to vary a gear ratio. Referring to Figure 4, spacer rings 21 are provided at outermost ends of the torque tube 17, thereby limiting radial movement of the ellipsoid planets 19 beyond the torque tube 17. The spacer rings 21 are also illustrated more clearly in Figure 11. The spacer rings 21 limit the distance between the two rows of ellipsoid planets 19 to less than the diameter of the torque tube 17, thus ensuring that the ellipsoid planets 19 cannot fly out radially past the torque tube 17. The angle between the centres of the two planetary shafts 18 and the torque tube 17 may be configured to approximately 120 degrees. This is illustrated in Figure 6. The wedging action greatly enhances the force between the planets and the torque tube 17. The major problem with friction gearing arises from the fact that it is impossible to force components together with increasing force if they are mounted on fixed shafts. The aforementioned configuration of the present disclosure overcomes this as the two planetary shafts 18 are not mounted directly on the planet carrier.

The splined drum 3 is disposed between and parallel to first and second planetary cone assemblies. The splined drum 3 is configured to bear the series of inverted vee-rings 6 on an outer circumferential surface of the drum 3. The vee-rings 6 are splined onto the drum 3 so as to be configured to slide along the drum 3. Referring to Figure 4d, the apertured ellipsoid planets 19 are configured to alternate with the series of inverted vee-rings 6, each vee-ring 6 and each ellipsoid planet 19 constituting a separate epicyclic gear train, the vee-ring 6 being the sun gear and the ellipsoid planet 19 being the inner planet. The vee-rings 6 are configured to be compressed together thus forcing the ellipsoid planets 19 radially outwards.

Screws may be inserted at the ends of the cylindrical drum 3 to keep the end rings 8 in place. The pressuriser ring 4 may be configured to move in both directions to take care of the situation during braking when the load drives the motor. However, the amount of movement in each direction may be configured to be minimal to avoid too much backlash.

Figures 4a and 4b show the pressuriser ring 4 in more detail, according to an embodiment of the present disclosure. Figure 4a shows a broadside view of the pressuriser ring 4 with four ball bearings 5 on one side and four ball bearings 5 on the other side. Figure 4b is a magnified view of how a section of the pressuriser ring 4 engages with the two cam rings 7 on either side of it. The pressuriser ring 4 and the splined driver are disposed on the main shaft 1 and configured to rotate with the main shaft 1. The the two cam rings 7 are disposed on the cylindrical drum 3. There are inclines inside the pressuriser ring 4 mirroring the inclines on the cam rings 7. The ball bearings 5 may be staggered on each side of the cam rings 7 to save space. The ball bearings 5 move a considerable distance into the cam rings 7 but cannot be pushed through from one side to the other. The pressuriser ring 4 illustrated in Figures 4a and 4b has eight ball bearings, four on each side. However, the present disclosure is not limited thereto, and more ball bearings may be used to withstand the very 10 high pressure. In Figure 4a note the two opposite grooves into which fit the ends of the splined driver 2. The ball bearings 5 run in deep grooves in the pressuriser ring 4 represented by the dotted lines in Figure 4b. Figure 4b shows how the ball bearings 5 protrude through the other side of the cam rings 7 and to accommodate this profusion circular grooves may be cut into the two cam rings 7.

Figure 4c is a schematic drawing of how the pressuriser ring 4 works, according to an embodiment of the present disclosure. The drawing on the left of Figure 4c shows the central pressuriser ring 4 itself, the ball bearings 5 and the cam rings 7 on each side of it closed up totogether. The drawing on the right of Figure 4c shows the pressuriser ring 4 remaining in the same position but the two cam rings 7 moving up in unison as they are splined to the drum. The pressuriser ring 4 is not splined to the drum 3. The ball bearings 5 roll between the inclines on the cam rings 7 and the inclines on the pressuriser ring 4. In Figure 4c the bearings on the left rotate clockwise and those on the right anticlockwise. The result of this is that the cam rings 7 on each side of the pressuriser ring 4 are forced apart. If there was no resistance to this sideways movement then the ball bearings 5 would roll off the cam rings 7. When the cones 22 are hard against the reaction rings 25 and the vee-rings 6 have compressed the ellipsoid planets 19 out against the torque tubes 17 a stage is reached when there is no more give. This then is the ideal setup. The ball bearings 5 will not have moved any appreciable distance along the inclines. The drum 3 and its vee-rings 6 are the end of the gear train and is the output, but because the pressuriser ring 4 is between the drum and the output shaft the rotating drum 3 not only drives the output shaft but by virtue of the pressuriser ring 4 compresses the vee-rings 6 together. The greater the load the transmission encounters the greater the pressure. Regarding the schematic, the ball bearings 5 in practice may be staggered each side of the pressuriser ring 4. Figure 4b shows how the ball bearings 5 are staggered each side of the pressuriser ring 4.

Figure 4d is a schematic of the interactions of the various components resulting from the rings each side of the pressuriser ring 4 being forced apart as mentioned in the description of Figure 4c. Note that if the pressuriser ring 4 exerts a force of F units each side then the total radial force is 20F units and each cone will press against its respective reaction ring 25 with 10F units of force. This is for a vee-ring of 90 degrees. If less than 90 degrees the outward force is less but if more than 90 degrees the outward force is greater. If more vee-rings and ellipsoids were used there would be an even greater force.

The above described configuration makes for a very compact, easy to assemble unit. The main components may be loaded onto the main shaft 1 in sequence. Having inserted the driver 2 in the slot 3a, the first component to be fitted on the main shaft 1 may be the splined cylindrical drum 3. In this regard, the splined cylindrical drum 3 may be configured to slide on the main shaft 1. The pressuriser ring 4 may be next to be fitted followed by a cam ring 7 each side of it, then the vee-rings 6 and lastly the end rings 8.

Figure 5a illustrates two half planet carriers 11 in which the twin planetary cone assemblies are mounted. Each half planet carrier 11 can be considered to be an integrally formed half-carrier/rotor combination, as illustrated in Figure 5a. Referring to Figure 5a, a rotor disc 32 is connected to one half of a planet carrier 11 by a tubular extension 33, forming one discrete structure. Figure 5a also shows two deep groove angular contact ball bearings 9. The deep groove angular contact ball bearings 9 may be configured to withstand a high axial load and ensure that disc magnets are kept at the correct distance from the stator poles. This air gap distance may be of the order of 1 - 2 millimetres. Rods 12 connecting the half planet carriers 11 also keep the rotor discs 32 at the requisite distance from each other. This relieves the pressure on the ball bearings 5.

Figure 5a shows a mount and bearing arrangement 14 for the planetary cones

22. The mount and bearing arrangement 14 may comprise a T-shaped 12 junction. The planetary cones 22 are configured to rotate in a hole through the centre thereof forming a bearing mount, which may be in the form of a bush bearing or a needle roller bearing. The end of the T-shaped junction may be rectangular in section capable of sliding outwards in a rectangular slot in the half planet carriers 11 but incapable of turning. Two cylindrical extensions on each side of the T-shaped junction bear against the flat disc of the half planet carriers 11 keeping the planetary cones 22 aligned.

Figure 5b illustrates twin planetary cone assemblies comprising first and second planetary cone assemblies 17, according to embodiments of the present disclosure. Two embodiments are illustrated in Figure 5b. In both embodiments, a torque tube 17 is attached to a planetary cone 22 at either end thereof, wherein the slant height of the planetary cone 22 is parallel to a main axis of the torque tube 17. In one aspect, the torque tube 17 and planetary cones 22 may be attached to each other with no conical rings. This makes for easy assembly, but as there would only be one point contact the joint would not wear well. Referring to Figure 5b, the main part of the planetary cones 22 is neither inside nor outside of the torque tube 17. The end of each of the planetary cones 22,

i.e., the vertex, forms part of the joint which can be inside (bottom drawing) or outside (top drawing) of the torque tube 17. In the latter case, the end is flared out over the torque tube 17, as illustrated in the top drawing in Figure 5b. The joint is basically the same for both and they operate on the cone principle where all projecting lines from conical surfaces converge at a common point, ensuring line contact.

Acccordingly, referring to Figure 5b, there are two conical rings 17a on each side of the torque tube 17. In one embodiment, the conical rings 17a are outside the torque tube 17 for a fixed angle joint outside the torque tube 17, as illustrated in the top drawing of Figure 5b. In another embodiment as illustrated in the bottom drawing of Figure 5b, the conical rings 17a are inside the torque tube 17. As these joints are subjected to very high stresses, line contact is important. The planetary cones 22 themselves have two conical surfaces at 13 their narrow end to roll on the two conical rings 17a of the torque tube 17. This pure rolling motion depends on the cone principle. The axes of the planetary cones 22, torque tube 17, and the vertices of all the conical rings intersect at a common point. If the line contact is not long, i.e., if the annular thickness of the conical rings is relatively small, the joints can be assembled. Otherwise they may have to be permanent. For example with the inner fixed joint, if the internal diameter of the conical rings were made smaller and the neck of the planetary cone 22 itself made smaller, longer line contact is achieved but the joint could not be dismantled.

Referring to the bottom drawing of Figure 5b, the inner fixed joint looks like a spool on the end of the planetary cones 22. The inner surfaces of the spool are conical. The torque tube 22 has just one conical ring 22a inside, the ring being conical on both sides.

Referring to the top drawing of Figure 5b, the joint on the outside of the torque tube 17 is basically the same as the inner fixed joint. With the outer joint, there is a spool comprising two conical rings 17a outside the torque tube 17 and a conical ring 22a on each side attached to the planetary cone 22.

If a is the vertical angle of the conical rings 17a on the torque tube 17, and β is the vertical angle of the conical ring 22a on the planetary cones 22, then α < β for the outer joint (top drawing in Figure 5b), and α > β for the inner joint (bottom drawing in Figure 5b). That is, for the outer joint, the planetary cones 22 drive the torque tube 17 faster, and for the inner joint, the planetary cones 22 drive the torque tube 17 slower.

Figure 6 illustrates an end view of the transmision mechanism, according to an embodiment of the present disclosure. The most important thing to note here is that spools 20 are diametrically opposite and that the torque tubes 17 are inside the spacer rings 21. The clearance can be small but there does need to be some clearance as the torque tubes 17 and spacer rings 21 rotate in opposite directions, and otherwise may clash.

Figure 7 is a perspective view of an outer casing for the transmision mechanism, according to an embodiment of the present disclosure. Referring to Figure 7, the outer casing comprises two half-casings, a half-casing 23 with a grooved edge, and a half-casing 24 with a hemispherical edge. Each of the half-casings 23 and 24 are shaped like two deep saucepans with six holed lugs 34 at the bottom ends. Three longitudinal channels 35 are cut into each half casing at 120 degree intervals. Reaction rings 25, as illustrated in Figure 8, slide in these channels via ring stub roller bearings 29. The half-casings 23 and 24 may be attached together using any suitable means. For example, referring to Figure 9, six thru-bolts 16 threaded through the lugs 34 may be configured to attach the half-casings 23 and 24 together.

As mentioned above, the rods 12 join the half planet carriers 11. The rods 12 may be configured to carry idler planets 13, as illustrated in Figure 6, which bear against the ellipsoid planets 19 keeping the assembly from skewing. It is very important to note that because of the spacer rings 21 the ellipsoid planets 19 cannot be forced out past the torque tubes 17. Therefore, the whole assembly consisting of two planetary cones 22, torque tube 17, and two shafts full of ellipsoid planets 19 are forced out en bloc and only stop when the planetary cones 22 hit the reaction rings 25. Figure 4d shows how this is achieved.

Figure 9 is an end view of electric motors 26 on the outer casing for controlling the spacing of the reaction rings 25 and consequently the gear ratio, according to an embodiment of the present disclosure. Referring to Figure 9, three small motors 26 may be connected together by an internally toothed belt 28 (like a car engine’s timing belt) running on six sprocket wheels.

The electric motors 26 on opposite sides of the outer casing control the spacing of the reaction rings 25 and consequently the gear ratio. Each electric motor may comprise a small stepper motor which has oppositely threaded screws on each side. The electric motors 26 may be configured to rotate inside nuts on the ends of the reaction rings 25. Depending on the direction of the motor’s rotation, the reaction rings 25 come closer together or go further apart. A minimum of two such linear actuators, spaced at 180 degrees are necessary to ensure that the reaction rings 25 move in unison.

Channels cut into the main shaft 1 supply power to the stator via three slip rings mounted on the main shaft 1.

Figure 10 illustrates an infinitely variable transmission system according to an embodiment of the present disclosure. Figure 10 shows most of the components described previously. However, some components have been left out in order not to obscure other components. Figure 11 shows the same components but with one extra component, namely an idler planet 13.

Referring to Figure 10, the assembly has two planetary shafts 18 bearing a number of freely sliding apertured ellipsoid planets 19. Ellipsoids are used in preference to spheres as more can be packed on a given shaft. In addition, ellipsoid planets (generated about their minor axis) will not tend to become skewed beween the vee-rings unlike a sphere. An end ring 8 at each distal end of the cylindrical drum 3 constrains outer movement of the vee-rings 6. Each planetary cone 22 is mounted in a bearing mount which can itself roll and slide outward in its slot and at the same time keep the planetary cone 22 properly aligned. Referring to Figure 5, an idler planet 13 may be mounted on each rod 12 to keep the entire twin planetary cone assembly aligned.

Figure 10 illustrates a detailed view of the main components, especially the pressuriser ring 4. Figure 4b shows a magnified view of how it works, as has been previously described. One of the easiest ways to understand how it works 16 is to take the case during braking where the load drives the input. Referring to Figure 10 if one turns the main shaft 1 it will also turn the pressuriser ring 4 because the driver 2 is connected and splined to both. Via the ball bearings 5 the pressuriser ring 4 will turn the drums 3 and the vee-rings 6 splined onto it and at the same time via the cam rings 7 incline compressing the vee-rings 6 each side. The ellipsoids 19 are squeezed out and the whole twin cone planet assembly is forced onto the reactions rings 25.

The electrically driven planetary cone transmission assembly of the present disclosure has several advantages over designs where input power is from another source. As the motor ‘stator’ is not fixed, use is made of the backward torque of the stator to compress the vee-rings and augment the forces driving the planet assemblies outwards. Many planetary designs can go from forward to reverse in one movement of the reaction rings. However, being electrically driven, one can simply reverse the rotation of the motor for reverse motion. This saves valuable ratio range. In this design, geared zero or neutral is when the reaction ring is at the cone larger diameter. The assembly is basically an electric motor completely enveloped by the transmission.

The assembly may have a number of longitudinal grooves for accommodating ball bearings and freely sliding vee-rings. Inside the stator besides the rotor is a pressuriser mechanism. The purpose of any machine such as this is to drive a load, and via the pressuriser mechanism the load further compresses the veerings. The assembly uses three different forces to force the twin planet cone assemblies out onto the reaction rings. The three forces are:

1. backward stator torque of the electric motor

2. load torque

3. centrifuigal force

The unit does not require any springs as many planetary cone transmissions require. The ellipsoid planets 19 may be truncated slightly to their minor axes so that part of the ellipsoid planets 19 are cylindrical and therefore roll on the torque tubes 17 by line contact.

Figure 11 is the same as Figure 10 except that it shows one of the idler planets

13. The idler planet 13 may be mounted on a rod or shaft 12 which also doubles as a connecting rod between the half planet carriers 11. The idler planet 13 and its shaft 12 look like a baker’s rolling pin with a bearing at each end.

Figure 12 shows a complete twin cone planet assembly comprising two planetary cones 22, one torque tube 17, two planetary shafts 18 bearing ellipsoid planets 19, two spacer rings 21, and two bearing/mounts 14. The system according to the present disclosure may comprise three such assemblies. Note the rectangular end on the bearing/mount 14. This is to allow the assembly to slide out radially but to prevent the bearing/mount turing 14 in its slot. Here the fixed angle joint is outside the torque tube 17.

This class of transmission is not only continuously variable but infinitely variable as well, i.e. it gives neutral or geared zero. Continuously variable transmissions can be adapted to become infinitely variable but they require an extra gear set.

There are four main configurations for this transmission system; the differences lie solely in the means by which the vee rings are compressed, and how the power is fed into the motor.

Thus, the differences are confined to the very core of the system i.e. the motor drum. Regarding the power supply, two of the configurations employ slip rings and brushes for the power feed, because the starter is fixed to the rotating drum. The other two configurations do not have slip rings but employ an extra component in the form of a concentric tube connecting the stator to the stationary casing.

Figure 14 shows a ring ensemble of 10 vee-rings 6, and inner cam rings 7 with an incline on one side rotate en bloc with the rest of the vee-rings 6. The end cam rings 7 are bolted to the drum 3. In the embodiment of Figure 14, a driver is not required for this configuration. Furthermore, in the embodiment of Figure 14, the vee-rings 6 are configured to be compressed together from distal ends of the drum 3 towards a centre of the drum 3 thus forcing the ellipsoid planets 19 radially outwards

These ball-connected rings have many coupling ball bearings which roll in semicylindrical channels and can be compressed together like a concertina. If there were 10 rings with ten semi-cylindrical channels on each side there would be 100 coupling balls. Each ring shares coupling balls with its neighbour. No ring can rotate relative to its neighbour, that is, the 10 rings in Figure 14 are configured to rotate en bloc on the drum 3. These rings are not internally splined unlike an alternative design where they are splined to slide on a splined drum, as per the previously described embodiment. A drum 42, as illustrated in Figure 15, may be configured to have a uniform outer circumferential surface. That is, the drum 42 may be configured to be smooth on the outside and the ring ensemble is free to rotate on the drum 3. While this ring ensemble which terminates in cam rings is free to rotate on the drum 3 it is desired not to have it rotate to any appreciable extent. This is because the ring ensemble should drive the cam rings attached to the drum 3, via the pressurizing balls, with as little free play as possible to avoid backlash when braking. By means of the pressurizing ball bearings, which are distinct from the coupling ball bearings and the end cam rings at each end of the drum 3, the rotating ring ensemble not only causes the drum 3 and hence the output to rotate, but also causes the ring ensemble to be pressurized. This in turn forces the ellipsoid planets 19 and the rest of the twin planetary cone assembly out radially.

As this design does not make use of the motor drum’s back torque - the stators are really stationary being connected to the casing - initial pressure can be obtained by having the rings magnetised or magnetic material therein.

Alternatively, wave springs or Belleville washers of the same dimensions of the vee rings may be loaded onto the drum.

Initial pressure is necessary before the pressure generated by the load torque kicks in.

The large number of coupling ball bearings and the semi-cylindrical channels in which they roll makes the ring assembly more complex but it has the advantage in that the drum on which they are mounted is of simple construction. There are no splined grooves on the outside and no slots cut into it to accommodate a driver which is not required for this configuration. It is basically a cylinder mounted on the main shaft via a thick sturdy washer in the centre and these three items welded together to form an integral unit. The dotted lines in Figure 15 show its outline.

Figure 15 is basically the same as Figure 5a. With Figure 5a the stators (which are not shown) are attached to the drum at its centre. In the Figure 5a configuration the word stator is really a misnomer as it can rotate as well as the rotor. Because the drum being part of the output rotates, this requires the power to be fed through slip rings and accompanying brush gear. Figure 15 represents a configuration that avoids the use of slip rings, according to an embodiment of the present disclosure. Referring to Figure 15, stators 43 are not attached to a drum 42 but are held steady by tubular extensions at each end which are connected to the casing via splines at the outer ends of the tubular extensions. The drum 42 is non-slotted and non-grooved and may be mounted on the main shaft 1 via a solid cylindrical disc 42a In this manner, the drum 42, disc 42a, and main shaft 1 are attached together and rotate as one component. The only real difference between Figure 5a and Figure 15 is the tubular extensions which are disposed between the main shaft 1 and the planet carrier I rotor combination. An extra race of bearings at each end of this tubular extension may also be necessary. Power is fed into the stator via channels cut into the tubular extensions.

Figures 16a to 16e illustrates various vee rings with semi-cylindrical channels on each side that can be used in the configuration of Figure 14, according to embodiments of the present disclosure. These vee-rings are not internally splined. The vee rings illustrated in the configuration of Figure 3 have no semicylindrical extensions and are internally splined. The vee-rings are not splined but have the aforementioned extensions.

Figure 16a shows one side of a ring with semi-cylindrical extensions or projections. The other side has similar projections as shown in Figure 16b. A broadside view showing the positions of the coupling ball bearings is shown in Figure 16c. The rings at their maximum spacing are shown in Figure 16d. Figure 16e shows the rings at their minimum spacing, i.e., when the twin planetary cone assemblies are hard against the reaction rings and can go out radially no further.

The distance between the maximum and minimum spacing need not be very large as the components can be manufactured so that at the maximum spacing the components are virtually fully compressed. All that matters is that they have the potential to be pressurized and compressed.

The words comprises/comprising when used in this specification are to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers , steps, components or groups thereof.

Claims

1. An infinitely variable multi-epicyclic friction transmission system for an electric motor, the system comprising:

a main shaft;

a plurality of twin planetary cone assemblies disposed parallel to the main shaft, each planetary cone assembly comprising:

a torque tube constituting a common outer planet attached to a planetary cone at either end, wherein the slant height of the cone is parallel to the main shaft;

a plurality of planetary shafts disposed adjacent and parallel to the torque tube, each planetary shaft configured to bear a series of slidable apertured ellipsoid planets, a spacer ring provided at each distal end of the torque tube to limit radial movement of the ellipsoid planets past the torque tube;

a drum disposed between and parallel to the planetary cone assemblies, the drum configured to bear a series of inverted vee-rings on an outer circumferential surface of the drum, wherein the vee-rings are configured to slide along the drum;

wherein the apertured ellipsoid planets are configured to alternate with the series of inverted vee-rings, each vee-ring and each ellipsoid planet constituting a separate epicyclic gear train, the vee-ring being the sun gear and the ellipsoid planet being the inner planet, wherein the vee-rings are configured to be compressed together thus forcing the ellipsoid planets radially outwards; and further comprising a reaction ring disposed around each planetary cone and configured to slide along the planetary cone to vary a gear ratio.

2. The system of claim 1, wherein the vee-rings are configured to be compressed together from a centre of the drum towards distal ends of the drum thus forcing the ellipsoid planets radially outwards.

3. The system of claim 2, comprising a pressuriser ring engaged with a splined driver on the main shaft, wherein the pressuriser ring and splined driver are disposed in the drum and located at a centre of the vee-rings with a subset of the vee-rings disposed at either side of the pressuriser ring and splined driver.

4. The system of claim 3, wherein the pressuriser ring comprises bearings configured to roll on cam rings disposed on the drum, wherein, when the main shaft is rotated, the bearings roll on the cam rings forcing the cam rings to move longitudinally along the drum and compress the vee-rings, forcing the ellipsoid planets radially outwards.

5. The system of claim 3 or 4, wherein the drum defines a slot in a centre portion thereof, the pressuriser ring and splined driver disposed in the slot.

6. The system of any preceding claim, wherein the drum is splined such that the vee-rings are configured to slide along the drum.

7. The system of claim 1, wherein the vee-rings are configured to be compressed together from distal ends of the drum towards a centre of the drum thus forcing the ellipsoid planets radially outwards.

8. The system of claim 7, comprising an end cam ring disposed at each of distal ends of the drum and fixedly attached to the drum.

9. The system of claim 7 or 8, comprising an inner cam ring for each vee-ring configured to rotate with the rest of the vee-rings.

10. The system of any of claims 7 to 9, wherein the drum has a uniform outer circumferential surface and is mounted on the main shaft via a solid cylindrical disc, such that the drum, disc, and main shaft are attached together and rotate as one component.

11. The system of any preceding claim, wherein each planetary cone assembly is configured to move out radially away from the main shaft.

12. The system of any preceding claim, wherein the plurality of twin planetary cone assemblies are mounted in a planetary carrier.

13. The system of claim 12, wherein the plurality of twin planetary cone assemblies are configured to move out radially in slots in the planetary carrier.

14. The system of claim 12 or 13, wherein the planetary carrier comprises two half-carriers coupled to each other and mounted on the main shaft.

15. The system of any preceding claim, comprising an idler planet to keep each twin planetary cone assembly aligned.

16. The system of any preceding claim, comprising between three and six twin planetary cone assemblies.

17. The system of any preceding claim, comprising two planetary shafts.