GB2567745A

GB2567745A - Infinitely variable multi-epicyclic friction transmission system for electric motor

Info

Publication number: GB2567745A
Application number: GB1815192.8A
Authority: GB
Inventors: Mcanulla Aidan
Original assignee: Individual
Current assignee: Individual
Priority date: 2017-09-18
Filing date: 2018-09-18
Publication date: 2019-04-24
Anticipated expiration: 2038-09-18
Also published as: GB2566528A; 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 is parallel to the main shaft. A plurality of planetary shafts 18 are disposed adjacent and parallel to the 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 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 and slides, via links 47 and reaction ring 46, along the planetary cone 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

Infinitely Variable Multi-epicyclic Friction Transmission System for Electric Motor

Field

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 2 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 pair of discs 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 with internal tubular extensions 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 1, 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 planents are loaded about a main shaft;

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

Figure 4c illustrates compression of the vee-rings forcing the ellipsoid planets radially outwards, according to an embodiment of the present disclosure;

Figures 5 and 5a illustrate two half planet carrier/rotor combinations joined together by rods and also the components of an axial flux motor, according to an embodiment of the present disclosure;

Figure 5b shows how the planetary cones are positioned, according to an embodiment 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 how all the outer components are configured and encased according to an embodiment of the present disclosure;

Figure 8 illustrates two views of a reaction ring according to an embodiment of the present disclosure;

Figure 9 illustrates an infinitely variable transmission system according to an embodiment of the present disclosure;

Figure 10 shows a complete twin cone planet assembly comprising two cones, one torque tube, two shafts of ellipsoids, and two spacer rings, according to an embodiment of the present disclosure; and

Figure 11 is an exploded view of most of the components used in the transmission, according to an embodiment 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.

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: compnsing:a main shaft; a plurality of twin planetary cone assemblies disposed parallel to the main shaft, each planetary cone assembly comprising: a torque tube; a planetary cone at each end of the torque tube and configured to roll inside the torque tube, wherein a slant height of the planetary cones 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 cylindrical drum disposed between and parallel to the planetary cone assemblies, the cylindrical drum configured to bear a series of inverted veerings on an outer circumferential surface of the cylindrical drum, wherein the vee-rings are configured to slide along the cylindrical drum; wherein the apertured ellipsoid planets are configured to alternate with the series of inverted vee-rings, 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 pair of discs 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 throughout 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 by sliding out along the cone shafts while at the same time two hemispheres at the end of the planetary cones slide further into the torque tube. Each of the planetary cones at each end of the torque tube is configured to roll inside the torque tube via the two 6 hemispheres that terminate each of the planetary cones. Each twin planetary cone assembly may comprise two largely hollow cones inside a torque tube, along with a plurality of planetary shafts for bearing ellipsoid planets and two spacer rings as illustrated in Figure 11. The two planetary 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.

One of the main aims of this transmission is to transmit sufficient power and torque by rolling friction alone, indeed, sufficient torque to go directly to the wheels without the use of a final drive in the form of a robust toothed gear wheel. This may seem a tall order for a friction drive until one sees that each epicyclic gear set has its internally splined vee ring splined onto a drum and it and several others with intermediate ellipsoids are compressed together in an analogous way to a multi-plate clutch. The power/torque is multiplied by the number of such gear sets. A vee ring presses on an ellipsoid, the ellipsoid presses on its neighbouring vee ring and it in turn on its neighbouring ellipsoid and so on. When these vee rings are compressed together, the outer planets and ring gears will also move axially. However, the outer planets in the form of rollers do not have to move axially. Unlike the inner planets which are sandwiched between the vee-rings they are under no such restriction. The inner planets can slide along the outer surface of the rollers leaving them in the same position in 3D space. In other words, the outer planet rollers can be joined together in the form of a long cylinder. Hence this cylinder or torque tube is the common outer planet of all the gear sets. Since the outer planet is in the form of a cylinder, only one ring (the reaction ring) is required to keep all components from flying out radially. However, two such rings are used, one on each side.

The vee-rings and the intermediate ellipsoid planets are configured to be compressed and the ellipsoid planets forced out radially. Such compression 7 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 5a illustrate 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 disks 3b are disposed internally towards the centre of the cylindrical drum 3 and are integral with the cylindrical drum 3 as shown by the dotted lines in Figure 1a. The holed disks 3b have long tubular extensions 43a on each side shown by the dotted and continuous lines in Figure 1a. The cylindrical drum 3, holed disks 3b and tubular extensions 43a may be all welded together as one integral unit. The cylindrical drum 3 is externally splined 31 to receive a number of sliding vee-rings. This unit is at the very centre of the tramsmission and is mounted in a casing via the two tubular extensions 43a. One of the tubular extensions 43a has three slip rings 38 to feed power into the motor, as illustrated in Figure 1a. This is because the motor acts in a differential mode, i.e. both “stator” and rotor can rotate. Channels cut into the tubular extensions 43a have conductors connected to the slip rings 38. Slots 3a are defined in two opposite sides of the centre of the cylindrical drum 3. Referring to Figure 2, an internally splined driver 2 is configured to be disposed in a centre portion of the cylindrical drum 3. The internally splined driver 2 is configured to be attached to a main shaft 1 as illustrated in Figure 1b. The internally splined driver 2 is thus configured to rotate with the main shaft 1. The main shaft 1 may be threaded through the internally splined driver 2 . Splines 35 may be defined on the main shaft 1 to engage the internally splined driver 2. The internally splined driver 2 may be in the shape of an elongated rhombus or diamond shape. When disposed in the centre of the cylindrical drum 3 and on the main shaft 1, ends of the internally splined driver 2 may protude through the slot 3a. It will be seen in Figure 1a that there is ample space on each side of the cylindrical 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 8 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. Refering to Figure 1a, inverted vee-rings 6 are configured to slide longitudinally along an outer circumference of the cylindrical drum 3. Reference numeral 37 indicates tapped drillings in the cylindrical drum 3 for end ring retaining bolts 39.

No bearings are required between the main shaft 1 and the tubular extensions 43a because the main shaft 1 and tubular extensions 43a of the motor stator 43, which itself is attached to the cylindrical drum 3, rotate at virtually the same speed and so one can be a sliding fit inside the other with a film of grease therebetween. It is only during pressurising of the vee-rings 6 that one can rotate relative to the other.

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 internally splined driver 2 at a centre of the series of veerings 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. The end rings 8 may be disposed at each of distal ends of the cylindrical drum 3 and fixedly attached to 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 roller bearings 5 is slid onto the centre of the cylindrical drum 3 it engages with the internally splined driver 2 which is fixedly attached to the main shaft 1. A cam ring 7 is disposed on the cylindrical drum 3 on each side of the 9 pressuriser ring 4. If the main shaft 1 is rotated in one direction and then in the other direction the pressuriser ring 4 will move several degrees each way. The movement of the internally splined driver 2 and pressuriser ring 4 is limited by the width of the slots 3a and the cylindrical drum 3. The roller bearings 5 of the pressuriser ring 4 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 of the pressuriser ring 4 roll on the inclines of the cam rings 7 forcing the cam rings 7 to move longitudinally along the cylindrical drum 3 and compress the vee-rings 6, forcing the ellipsoid planets 19 radially outwards. This is illustrated in Figure 4c especially. Refering to Figure 4c, each planetary cone assembly comprises a torque tube 17 constituting a common outer planet attached to a planetary cone 22 at each 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 10.

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 be approximately 120 degrees. This is illustrated in Figure 6. The wedging action greatly enhances the force beteween the ellipsoid planets 19 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 carriers 11.

The cylindrical drum 3 is disposed between and parallel to first and second planetary cone assemblies. The cylindrical drum 3 is configured to bear the series of inverted vee-rings 6 on an outer circumferential surface of the cylindrical drum 3. The vee-rings 6 are splined onto the cylindrical drum 3 so as to be configured to slide along the cylindrical drum 3. Referring to Figure 4c, the 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 rotate 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 eight roller bearings 5 and pressuriser ring stubs 13 mounted on its circumference. 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 internally splined driver 2 are disposed on the main shaft 1 and configured to rotate with the main shaft 1. The two cam rings 7 are disposed on the cylindrical drum 3. . The pressuriser ring 4 illustrated in Figures 4a and 4b has eight roller bearings 5. However, the present disclosure is not limited thereto, and more roller bearings 5 may be used to withstand the very high pressure. In Figure 4a note the two opposite grooves 28 into which fit the ends of the internally splined driver 2.

Figure 4c is a schematic drawing of how the pressuriser ring 4 works, according to an embodiment of the present disclosure. The pressuriser ring 4 is not splined to the cylindrical drum 3. 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 roller bearings 5 would roll off the cam rings 7. When the planetary cones 22 abut the reaction rings 25 and the veerings 6 have compressed the ellipsoid planets 19 out against the torque tube 17 a stage is reached when there is no more give. This then is the ideal setup. The roller bearings 5 will not have moved any appreciable distance along the inclines. The cylindrical 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 cylindrical drum 3 and the main shaft 1 the rotating cylindrical drum 3 not only drives the main shaft 1 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.

Figure 4c is a schematic of the interactions of the various components resulting from the cam rings 7 each side of the pressuriser ring 4 being forced. Note that if the pressuriser ring 4 exerts a force of F units each side then the total radial force may be 20F units and each planetary cone 22 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 greater than 90 degrees the outward force is greater. More vee-rings and ellipsoids results in 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 internally splined driver 2 in the slot 3a, the first component to be fitted on the main shaft 1 may be the cylindrical drum 3. In this regard, the 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.

Figures 5 and 5a illustrates two half-planet carriers 11 in which the twin planetary cone assemblies may be mounted. Each half-planet carrier 11 can be considered to be an integrally formed half-carrier/rotor combination, as illustrated in Figure 5. Referring to Figure 5, a rotor disc 32 is connected to one half of a planet carrier 11 by a tubular extension 33, forming one discrete structure. Figure 5 also shows two deep groove angular contact ball bearings 9 and roller bearings 10. 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 9.

Figure 5b shows the planetary cones 22 and how they are positioned in the torque tube 17. The planetary cones 22 define two hemispheres 27 integral with the planetary cones 22 and disposed at one end of each of the planetary cones 22. Each of the planetary cones 22 at each end of the torque tube 17 is configured to roll inside the torque tube 17 via the two hemispheres 27 that terminate each of the planetary cones 22. The planetary cone 22 is mounted on a planetary cone shaft 49 so that the slant height of the planetary cone 22 is parallel to the central axis. The planetary cone shafts 49 may be configured to be flexible radially in order to ensure that both hemispheres 27 of the planetary cones 22 contact the inside of the torque tube 17. The top of Figure 5b shows one of the planetary cone shafts 49 detached from the half-planet carrier 11. The planetary cone shafts 49 may be welded 40 to the half-planet carriers 11 such that the planetary cone shafts 49 can bend radially but have great resistance to bending circumferentially. The planetary cone shafts 49 may be welded to the half-planet carriers 11 at an angle that ensures that the slant height of the planetary cones 22 is parallel to the central axis. However, if the planetary cone shafts 49 are fixed at an angle where the planetary cones 22 are slightly biased out radially, then by forcing the planetary cone shafts 49 in 13 radially and pushing then into the torque tube 17, the planetary cone shafts 49 can be slightly spring-loaded.

Referring to Figue 5a, channels cut into the tubular extensions 43a on the cylindrical drum 3 supply power to the stator via the three slip rings 38 mounted on the tubular extensions 43a.

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 between the torque tubes 17 and the spacer rings 21 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 may potentially clash.

Figure 7 shows how all the outer components are configured and encased. A very rigid structure is formed when two end plates 24 and six long bolts 16 are all tightly bolted together via bolt nuts 15. A control ring 46 is disposed at the centre with the reaction rings 25 on either side. The control ring 46 is mounted on the six bolts 16 via spool-type bearings 45 as shown in Figure 9.

Three links 47 each side of the control ring 46 connect the reaction rings 25 to the control ring 46. Turning the control ring 46 in either direction brings the reaction rings 25 closer together or further apart in unison, thereby varying the gear ratio. The control ring 46 may be operated by cable or a small part of its outer circumference may have spur gearing driven by a stepper motor. It is important to note that the bolts 16 are not of circular section but are concave (diagonally opposite) to match the curvature of ball bearings, as illustrated at the bottom of Figure 7. The control ring 46 cannot move longitudinally because of the spool-type bearings 45.

Referring to Figure 5, as mentioned above, the rods 12 join the half-planet carriers 11. 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 4c shows how this is achieved.

Figure 8 illustrates two views of a reaction ring 25 according to an embodiment of the present disclosure. Referring to Figure 8, the reaction ring 25 has six double ball bearing mounts 30. Ball bearings 50 are configured to rotate in the double ball bearing mounts 30 with very little friction. Figure 7 shows a section of a thru-bolt 16 which exactly fits the space between the balls. The links 47 are bolted onto threaded stubs 42 on either side of the control ring 46 via link bearings 48. Stub nuts 29 may be used to connect the links 47 to the control ring 46 and the reaction rings 45.

Figure 9 illustrates an infinitely variable transmission system according to an embodiment of the present disclosure. Referring to Figure 9, the system 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. Figure 9 also shows two of the long thru bolts 16 and the control ring 46 which is mounted on the bolts 16 via spool-type bearings 45. In addition, Figure 9 shows one of the links 47 connecting the control ring 46 to the reaction ring 25. Figure 9 also shows how the reaction rings 25 can slide along the bolts 16 via the ball bearings 50 in the double ball bearing mount 30. Figure 9 shows the thru-bolts 16 in contact with the ball bearings 50. Figure 9 also shows one of the six links 47 (3 on each side) connecting the control ring 46 to the reaction ring 25, whereby the gear ratio is varied by turning the control ring

46. Reference numeral 44 indicates a thru bolt bearing retaining pin.

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 10 shows a complete twin cone planet assembly comprising two planetary cones 22, one torque tube 17, two planetary shafts 18 bearing ellipsoid planets 19, and two spacer rings 21. The system according to the present disclosure may comprise three such assemblies. As described previously, the planetary cones 22 define two hemispheres 27 integral with the cones 22 and disposed at one end of each of the planetary cones 22.

Figure 11 illustrates a detailed view of the main components, especially the pressuriser ring 4. Figure 4b shows a magnified view of how the transmision operates, as has been previously described. One of the easiest ways to understand how the transmision operates is to take the case during braking where the load drives the input. Referring to Figure 11, rotation of the main shaft 1 will also turn the pressuriser ring 4 because the driver 2 is connected thereto. Via the roller bearings 5 the pressuriser ring 4 will both turn and compress the cam rings 7 and consequently 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. Reference numeral 23 indicates a pressuriser ring spring. A hole 26 is defined in the pressuriser ring 4 for the pressuriser ring spring 23. Reference numeral 36 indicates a casing bearing mount.

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 16 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 stator differs from a typical motor stator in that it is precision made and balanced.

The purpose of any machine such as this is to drive a load, and via the pressuriser mechanism the load further compresses the vee-rings. 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. centrifugal force

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.

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.

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;

a planetary cone at each end of the torque tube and configured to roll inside the torque tube, wherein a slant height of the planetary cones 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 cylindrical drum disposed between and parallel to the planetary cone assemblies, the cylindrical drum configured to bear a series of inverted vee-rings on an outer circumferential surface of the cylindrical drum, wherein the vee-rings are configured to slide along the cylindrical drum;

wherein the apertured ellipsoid planets are configured to alternate with the series of inverted vee-rings, 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 cylindrical drum is splined such that the vee-rings are configured to slide along the cylindrical drum.

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

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

5. The system of any preceding claim, comprising a pressuriser ring engaged with a splined driver on the main shaft, wherein the pressuriser ring and splined driver are disposed in the cylindrical 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.

6. The system of claim 5, wherein the pressuriser ring comprises bearings configured to roll on cam rings disposed on the cylindrical 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.

7. The system of claim 6, wherein the cam rings are disposed on the cylindrical drum on each side of the pressuriser ring.

8. The system of claim 5, 6, or 7, wherein the cylindrical drum defines a slot in a centre portion thereof, the pressuriser ring and splined driver disposed in the slot.

9. The system of any preceding claim, comprising an end ring disposed at each of distal ends of the cylindrical drum and fixedly attached to the cylindrical drum.

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

11. The system of claim 10, wherein the planetary carrier comprises two half-carriers coupled to each other and mounted on the main shaft.

12. The system of any preceding claim, wherein each of the planetary cones at each end of the torque tube is configured to roll inside the torque tube via two hemispheres that terminate each of the planetary cones.

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

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