GB2503282A

GB2503282A - Floating gear for transmission having friction and dog clutches on opposing sides

Info

Publication number: GB2503282A
Application number: GB1211160.5A
Authority: GB
Inventors: Pedro Zabala; David Kelly; Andrew Harrison; Mark Findlay; Alex Tylee-Birdsall
Original assignee: DRIVE SYSTEM DESIGN Ltd; Drive Systems Ltd
Current assignee: DRIVE SYSTEM DESIGN Ltd; Drive Systems Ltd
Priority date: 2012-06-22
Filing date: 2012-06-22
Publication date: 2013-12-25
Also published as: GB201211160D0

Abstract

A transmission system comprising at least one floating gear 16a, 18a rotationally mounted upon a first shaft 10. The system comprising a floating gear activation system for controlling torque transfer between the at least one floating gear 16a, 18a and the first shaft 10. The gear activation system comprising a first device having a friction interface 28 for frictional engagement with a friction interface 30 disposed on a first side of the at least one floating gear 16a, 18a and a second device having a locking interface 25 for an interpositional engagement with a locking interface 26 disposed on a second side, opposing the first side, of the at least one floating gear 16a, 18a. The floating gear is rotationally coupleable to the first shaft by the friction interface 28 and/or the locking interface 25. Preferably the activation system is located between a pair of floating gears 16a, 18a having a frictional engagement 28 associated with one of the gears 16a and a locking engagement associated with the second gear 18a (Figure 1). A method is disclosed where a database containing a control parameter is updated when a predefined amount of slip is produced by the transmission.

Description

TRANSMISSION SYSTEM

TECHNICAL FIELD

The present invention relates to a transmission system or gearbox, an activator for gear selection and a method of gear selection; particularly but not exclusively to an activator configured for frictional engagement with a gear and for locking engagement with a different gear.

BACKGROUND

It is known to provide vehicles with a transmission, also known as a gearbox, for providing speed and torque conversions between a rotating power source engine or motor, for example a crankshaft of an internal combustion engine, and a driveshaft coupled to one or more differentials which drive the road wheels.

A typical manual transmission comprises an input shaft and an output shaft. The input shalt is coupled to the crankshaft of an engine via a clutch and flywheel.

The output shaft is coupled to the drive wheels via a drive shaft and one or more differentials or additional gears.

The input shaft comprises a plurality of gears, normally helical gears, which are fixed to the input shaft. The output shaft comprises a plurality of gears, one br each of the gears on the input shaft, the gears on the output shaft are "floating" that is to say they are mounted on bearings so as to rotate freely about the output shaft.

The output shaft also comprises a plurality of activators fixedly mounted thereon, which rotate with the output shaft.

The activators comprise a locking mechanism for locking with a floating gear, typically a dog clutch.

It is known to combine a cone clutch with a dog clutch to create a synchroniser; the cone clutch engages first, in a frictional engagement with the selected gear to match the speed of the floating gear with the output shaft; once the speed is matched the activator is moved into locking engagement with the gear by engaging the dog clutch.

The activator may comprise a cone clutch and dog clutch on both sides for engagement with different gears.

The process of selecting or activating an individual gear comprises an initial friction stage that helps to synchronise gear and shaft speed. In this stage a sleeve provided on the activator pushes against a ring that blocks its way and this applies force to the friction interface.

When the speed is synchronous the blocking ring is pushed out of the way and the sleeve is free to continue its travel towards the gear. Once the blocking ring is moved, the synchroniser will not be able to generate any more friction unless the activator is returned to a neutral position and the process started again. If the initial speeds of the gear and shalt are synchronous, the friction phase will not be activated. After the friction phase is completed and the sleeve has travelled up to the locking interface of the gear, the locking phase takes place with the sleeve locking the gear to the shaft using the dog clutch. When returning the activator back to the neutral position the friction phase cannot be activated again and the only task performed is release of the gear, there is no control of torque or speed during the release stage.

SUMMARY

The present invention seeks to overcome or at least mitigate the problems of the prior art.

Whilst the present invention has particular application for vehicles, it is envisaged that the invention may be employed in other applications, for example it is foreseen that the invention may be employed in power generation, in pumping applications, marine applications and industrial applications.

A first aspect of the invention provides a transmission system comprising at least one floating gear rotationally mounted upon a first shaft, the system comprising a floating gear activation system for controlling torque transfer between the at least one floating gear and the first shaft, the gear activation system comprising a first device having a friction interface for frictional engagement with a friction interface disposed on a first side of the at least one floating gear, and a second device having a locking interface for an interpositional engagement with a locking interface disposed on a second side, opposing the first side, of the at least one floating gear, whereby the floating gear is rotationally coupleable to the first shaft by the friction interface and/or the locking interface.

Preferably, the transmission system comprises at least one further gear mounted upon at least one further shaft said at least one further gear being coupled to a respective one of the at least one floating gear on the first shaft.

Preferably, the at least one further gear is fixedly mounted on the second shaft for rotational movement therewith.

Alternatively, the at least one further gear is a floating gear rotationally mounted upon the second shaft.

Alternatively, the friction interface comprises a clutching mechanism.

Preferably, the clutch mechanism is a cone clutch, preferably a multi plate cone clutch.

Alternatively, the locking interface comprises a dog clutch.

Preferably, the first activator comprises a first and a second side, and the friotion interface is provided on the first side and a locking interface is provided on the second side for engagement with a different floating gear provided on the first shaft.

Alternatively, the first activator comprises a first and second side and the friction interface is provided on a first side and a second friction interface is provided on the second side for engaging with a different floating gear provided on the first shaft.

Alternatively, the second activator comprises a first and second side and the locking interface is provided on a first side and a friction interface is provided on the second side for engaging with a different floating gear provided on the first shaft.

Alternatively, the second activator comprises a first and second side and the locking interface is provided on a first side and a second locking interface is provided on the second side for engaging with a different floating gear provided on the first shaft.

A second aspect of the invention provides a device for a transmission system comprising: a first side; a second side, opposing the first side; a friction interface for frictional engagement with a friction interface of a first gear; a locking interface for an interpositional engagement with a locking interface of a second gear; wherein the friction interface is disposed on the first side and the locking interface is disposed on the second side.

Preferably, a transmission system comprises a device.

Preferably a vehicle comprises the transmission system.

A third aspect of the invention provides a method for activating a floating gear of a transmission system comprising: providing a first floating gear rotationally mounted upon a first shaft and a floating gear activation system for controlling torque transfer between the at least one floating gear and the first shaft, the gear activation system comprising a first device having a friction interface for frictional engagement with a friction interface disposed on a first side of the first floating gear, and a second device having a locking interface for an interpositional engagement with a locking interface disposed on a second side of the first floating gear, the second side opposing the first side; sliding the first device along the first shaft, in a first direction, into frictional engagement with the friction interface on first side of the first gear, transferring torque to the first floating gear from the first shaft so as to substantially synchronise the first floating gear with the first shaft, and then sliding the second device along the first shaft, in a second direction opposing said first direction, into locking engagement with the locking interface on the second, opposing, side of the first gear, whereby locking the first floating gear with the first shaft.

Preferably, the method for activating a floating gear of a transmission system comprises sliding the first device along the first shaft, in the second direction, so as to disengage the friction interface of the first device from the friction interface on the first side of the first gear.

A fourth aspect of the invention provides a method for shifting gear ratios of a transmission system comprising: providing a first floating gear rotationally mounted upon a first shaft and a floating gear activation system for controlling torque transfer between the first floating gear and the first shaft, the gear activation systcm comprising a first device having a friction interface for frictional engagement with a friction interface disposed on a first side of the first floating gear, and a second device having a locking interface for interpositional engagement with a locking interface disposed on a socond side of the first floating gear, the second side opposing the first side; providing a second floating gear rotationally mounted upon the first shaft and the gear activation system comprising a third device having a friction interface foi frictional engagement with a friction interface disposed on a first side of the second floating gear, and a fourth device having a locking interface for interpositional engagement with a locking interface disposed on a second side of the second floating gear, the second side opposing the first side; engaging the friction interface of the first device with the friction interface of the first floating gear by sliding the first device along the first shaft; disengaging the locking interface of the second device from the locking interface of the first floating gear by sliding the second device along the first shaft; engaging the friction interface 01 the third device with the friction interface of the second floating gear by sliding the third device along the first shaft; discngaging the friction interfaco of the first device with the friction interface of the first floating gear by sliding the first device along the first shaft; engaging the locking interface of the fourth device with the locking interface of the second floating gear by sliding the fourth device along the first shalt.

Preferably, torque is transferred from the first floating gear to the second floating geai while the friction interface of the first device is engaged with the friction interface of the first floating gear and the friction interface of the third device is simultaneously engaged with the friction interface 01 the second floating gear, whereby effecting a powershift between the first floating gear and the second floating gear.

Preferably, the method for shifting gear ratios comprises providing at least one further floating gear mounted upon the first shaft, the or each at least one further floating gear having a friction interface for frictional engagement with a respective friction interface of at least one further device, the method further comprising frictionally engaging one or more of the friction interfaces of the at least one further floating gears and simultancously engaging the friction interface of the third device with the friction interface of the second floating gear by sliding the third device along the first shaft.

A titth aspect of the invention provides a method for holding a vehicle on a hill comprising: providing a first floating gear rotationally mounted upon a first shaft and a floating gear activation system for controlling torque transfer between the first floating gear and the first shaft, the gear activation system comprising a first device having a friction interface for frictional engagement with a friction interface disposed on a first side of the first floating gear, and a second device having a locking interface for interpositional engagement with a locking interface disposed on a second side of the first floating gear, the second side opposing the first side; providing at least one further floating gear mounted upon the first shaft, the or each at least one further floating gear having a friction interface for frictional engagement with a respective friction interface of at least one further device; wherein the method comprises: frictionally engaging the friction interface of the first Iloating gear with the first device and/or engaging the locking interface of the first floating with the second device; and simultaneously engaging one or more of the friction interfaces of the at least one further floating gear with the respectivo friction intorf ace of the at least one further clovice.

A sixth aspect of the invention provides a method for shifting gear ratios of a transmission system comprising: providing a first floating gear rotationally mounted upon a first shaft and a floating gear activation system for controlling torque transfer between the first floating gear and the first shaft, the gear activation system comprising a first device having a friction interface for frictional engagement with a friction interface disposed on a first side of the first floating gear, and a second device having a locking interface for interpositional engagement with a locking interface disposed on a second side of the first floating gear! the second side opposing the first side; providing a second floating gear rotationally mounted upon a second shaft, the second floating gear being coupled to the first shaft by a further gear mounted on the first shaft and the gear activation system comprising a third device having a friction interface for trictional engagement with a fricthn interface disposed on a first side of the second floating gear, and a fourth device having a locking interface for interpositional engagement with a locking interface disposed on a second side of the second floating gear, the second side opposing the first side; engaging the friction interface of the first device with the friction interface of the first floating gear by sliding the first device along the first shaft; disengaging the locking intorfaco of tho socond device from the locking intcrfaco of thc first floating gear by sliding the second device along the first shaft; engaging the friction interface of the third device with the friction interface of the second floating gear by sliding tho third device along the second shaft; disengaging the friction interface of the first device with the friction interface of the first floating gear by sliding the first device along the first shaft; engaging the locking interface of the fourth device with the locking interface of the second floating gear by sliding the fourth device along the second shaft.

A seventh aspect of the invention provides a method for adapting the torque transfer function of a transmission system comprising: engaging a friction interface of first activator with a friction interface of the gear under test, disengaging a locking interface of a second activator from a locking interface of the gear under test; ieducing the force applied by the friction interface of the first activator to the friction interface of the gear under test, wheleby introducing a predefined degree of slip; recording a control parameter of the transmission system which produces the prodelinod dcgrce of slip; leceiving a parameter indicative of torque value delivered to the transmission system; interrogating a database to obtain a stored value of the control parameter corresponding to the value ol the parameter indicative of torque value delivered to the transmission system; comparing the stored value of the control parameter with the recorded value of the control parameter; updating the data base with the recorded value of the control parameter if different to the stored values; increasing the pressure between the friction interface of the first activator and the friction interface of the gear under test so as to synchronise the gear under test with the shaft upon which it is mounted; engaging a locking interface of the gear under test by activating the second activator to interpose the locking interface of the second activator with the locking interface of the gear under test; disengaging the friction interface of the first activator from the friction interface of the gear under test.

S

Preferably, the method comprises: detecting operation of the transmission system under stable conditions for a gear under test.

Preferably, the method comprises: waiting until steady state conditions are reached with micro slip between the friction interfaces.

Preferably, the method omits the step of, interrogating the database to obtain a stored value of the control parameter corresponding to the value of the parameter indicative of torque value delivered to the transmission system; with the step of, calculating a value of the control parameter corresponding to the value of the parameter indicative of torque value delivered to the transmission system.

Preferably, the method replaces the step of, comparing the stored value of the control parameter with the recorded value of the control parameter and the method, updates the database with the recorded value of the control parameter irrespective of whether or not the value is different to the stored value.

Preferably, the method reduces the force applied by the friction interface of the first activator to the friction interface of the gear under test, to introduce a predefined degree of micro-slip.

An eighth aspect of the invention provides a mechanism for moving an activator in a transmission system, which mechanism comprises a double acting cylinder having a double ended piston, the cylinder having a first port for fluid action on a first end of the piston and a second port for fluid action on a second end of the piston, the first port coupled to a first pressure control valve such that the mechanism can control the pressure or force applied when moving the piston in a first direction for engaging a friction interface of a transmission system, and the second port coupled to a direction control valve, such that the mechanism can control the direction of travel of the piston within the cylinder.

A ninth aspect of the invention provides a transmission system comprising a floating gear mounted upon a first shaft, the floating gear having a first side comprising a friction interface and a second side comprising a locking interlace, wherein a first activator is disposed adjacent the first side of the floating gear and comprises a friction interlace for Irictional engagement with the Iloating gear, a second activator being disposed on the second side of the floating gear and having a locking interface br interposition with the locking interface of the floating gear wherein the floating gear can be rotationally coupled to the first shaft by the first activator and/or the second activator.

A tenth aspect of the invention provides a transmission system comprising a device slideably mounted upon a shalt, the device comprising first side comprising a friction interface for frictional engagement with a friction interface of a floating gear provided on the shaft wherein the device comprises a body mounted upon a support in rolling or sliding contact therewith for movement along the shaft, the device having a resilient device whose biasing force must be overcome when moving the body in a direction for engagement of the friction interface with the friction interface of the floating gear.

Preferably, the body comprises a ramp or recess which borms a detent for resisting movement of the body with respect to the support.

Within the scope of this application it is envisaged that the various aspects, embodiments, examples, features and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings may be taken independently or in any combination thereof. For example, features described in connection with one embodiment are applicable to all embodiments unless there is incompatibility of features.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: FIGURE 1 schematically illustrates a cross-sectional view of a transmission system according to an embodiment of the present invention; FIGURE 2 is an enlarged view of a portion of Figure 1; FIGURE 3 is an enlarged view of a second portion ob Figure 1; FIGURE 4 is an enlarged view of a third portion of Figure 1; and FIGURE 5 is a schematic view of a transmission layout according to an embodiment of the invention; FIGURE 6 is a schematic view in cross section of a machine for applying an axial force to an activator; FIGURE 7 is a graph of pressure/force against current for a typical solenoid valve; FIGURE 8 is a schematic view in cross section of a device for overcoming hysteresis in a valve; FIGURE 9 is a graph of the pressure, position, torque transfer and slip of the friction interface with respect to time during a measurement cycle; and FIGURE 10 is a flowchart illustrating the steps of a method for adapting the torque transfer friction system of Figures ito 5.

DETAILED DESCRIPTION OF EMBODIMENTS

Detailed descriptions of specific embodiments of the transmission system, vehicle, activator and method of actuation of a transmission of the present invention are disclosed herein. It will be understood that the disclosed embodiments are merely examples of the way in which certain aspects of the invention can be implemented and do not represent an exhaustive list of all of the ways the invention may be embodied. Indeed, it will be understood that the transmission system, vehicle, activator and method of actuation of a transmission described herein may be embodied in various and alternative forms. The figures are not necessarily to scale and some features may be exaggerated or minimised to show details of particular components. Well-known components, materials or methods are not necessarily described in great detail in order to avoid obscuring the present disclosure. Any specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the invention.

Figure 1 illustrates a schematic representation of a transmission system 8 shown in cross section. The transmission system 8 comprises an input shaft 10 and an output shaft 12.

Input shalt 10 comprises a plurality of floating gears 1 4a, 1 Ga, 1 Ba. Floating gears 1 4a, 1 Ga, 1 8a are rotationally mounted upon the input shaft 10 by bearings 1 la. In this way rotation of the input shaft 10 does not rotate the floating gears 14a, 16a, 1 8a.

The output shaft 12 comprises a plurality of fixed gears 14b, 16b, lBb which synchronously rotate with the output shaft 12. Input and output shafts 10, 12 are rotationally mounted in a housing (not shown), the input and output shaft 10, 12 are mounted in the housing by bearings 5a, 5b respectively.

The floating gears 1 4a, 1 6a, 1 Ba, and fixed gears 1 4b, 1 6b, 1 Sb each comprise a plurality of teeth, and/or fixed gears. Preferably, the floating gears are helical gears, however in other embodiments other gear types are envisaged including but not limited to spur or straight cut gears or double helical gears.

The teeth of first floating gear 14a mesh or mate with the teeth of lirst fixed gear 14b. The teeth of second floating gear 1 Ga mesh with the teeth of second fixed gear 1Gb and the teeth of third Iloating gear 1 Ba mesh with the teeth of third fixed gear 1 8b.

The floating gears 14a, iSa, iSa are distributed along the input shaft 10 and the fixed gears 14b, 1Gb, 18b are distributed along the output shaft 12. The floating gears 14a, iSa, 18a are spaced apart from one another.

A double selector or activator 20 is provided between the first floating gear 14a and second floating gear 1 Ga, a second double activator 20 is provided between the second floating gear 1 6a and third floating gear 1 Ba.

A single selector or activator 19 is provided at a first end of the input shaft 10 adjacent to first the floating gear 14a.

A second single selector or activator 22 is provided at a second end of the input shaft 10 adjacent to the third floating gear 18a.

The double activators 20 and single activators 19, 22 are provided for coupling the floating gears 1 4a, 1 Ga, 1 8a to the input shaft 10 so that they rotate synchronously.

Double activator 20 comprises a first side 13 and a second side 15 as shown in Figure 2.

First side 13 comprises a first interface 28; first interlace 28 is a friction interface for frictionally engaging with a gear friction interface 30 of second floating gear 16a. In the illustrated embodiment the friction interlace optionally comprising a cone clutch, as illustrated in Figure 4. Preferably the friction interface is a multiple plate cone clutch, however in other embodiments other structure are envisaged.

The second side 15 comprises a locking interface 26 for locking engagement with a gear locking interface 25 of third floating gear 18a. The locking interface 26 comprises a plurality of dog teeth forming a dog ring which engage with a dog ring having dog teeth provided on the third floating gear isa for forming a dog clutch, the two dog gears being capable of mating or meshing together to form an interpositional fit.

Double activator 20 is capable of engaging with two different gears.

The double activators 20 and the single activators 19, 22 are slideably mounted upon the input shaft 10 so as to be slideable in an axial direction, for example using a spline 29. The double activator 20 can be moved along the input shaft 10 so as to engage and disengage the friction interface 28 with the gear friction interface 30, and to engage and disengage the locking interface 26 with the gear locking interface 25. The double activator 20 is provided with a neutral position, in which it is not engaged with either the second or third floating gears 1 Ga, 1 8a. That is to say that both the friction interface 28 and locking interface 26 are disengaged from the respective ones of the second or third floating gears 1 6a, 1 Ba.

When the double activator 20 is engaged with the third floating gear 1 Ba, as indicated by direction arrow L, the locking interface 26 creates a first torque path A from the input shaft 10 to the output shaft 12.

When the double activator 20 is engaged with second floating gear 1 6a, as indicated by direction arrow F, the friction interface 28 creates a second torque path B from the input shaft 10 to the output shaft 12.

Figure 3 illustrates the first single activator 19; first single activator 19 comprises a locking interface 26 for locking engagement with a gear locking interface 25 of first floating gear 14a.

The locking interface 26 comprises a plurality of dog teeth forming a dog gear which engage with a dog gear having dog teeth provided on the first floating gear 18a for forming a dog clutch, the two dog gears being capable of mating or meshing together to form an interpositional fit.

Figure 4 illustrates the second single activator 22; second single activator 22 comprises a friction interface 28, for frictionally engaging with a gear friction interface 30 of third floating gear 18a. In the illustrated embodiment the friction interface 28 comprises a cone clutch, as illustrated in Figure 4.

The first and second single activators 19,22 can slide along the input shaft 10 preferably on a spline 29.

The single activator 19 ensures that a locking interface 26 is provided for locking the first floating gear 1 4a to the input shaft 10.

The single activator 22 ensures that the third floating gear 1 8a can be in frictional engagement, via a friction interface 28, with the input shaft 10.

Figure 5 illustrates a transmission system for a vehicle in which each of the first and second double activators 20a, 20b are coupled to a respective one of a first or second 34, 35 actuators, preferably the first and second actuators 34, 35 each comprise forks having a pair of legs in a substantially U-shaped configuration. The legs of the forks extend at least partially about the circumference of their respective double activators 20. The double activators 20 are provided with a recess or channel extending circumferentially about at least a portion of the respective on of the first or second double activators 20a, 20b circumference for receiving the first or second actuator 34, 35 respectively.

In other embodiments the actuators 32a, 32b, 34, 35 The single activator 19 is coupled to a third actuator 32a again preferably of a fork arrangement.

Single activator 22 is coupled to a fourth actuator 32b, again preferably of a fork arrangement.

In other embodiments the actuators 32a, 32b, 34, 35 may have a different shape and configuration.

The third and fourth actuators 32a, 32b are coupled together by a shalt or rail 36, in this way the first and second single activators 19, 22 effectively operate as a double activator, which is to say provide both a locking interface and a triction interlace which are moved simultaneously, the friction interface engaging with a different gear to that engaged by the locking interface.

It will be appreciated that each floating gears 14a, isa, isa is activated or coupleable to the input shaft 10 by one, or both, of two different independent activators 19, 20, 22.

The floating gears 1 4a, 1 6a, 1 8a can be engaged by a friction interface 28 only, by a locking interface 26 only or by both a friction interface 28 and locking interface 26. The floating gears 14a, 16a, 18a may not be engaged by either the friction or locking interfaces 28, 26, that is to say they are free to rotate with respect to the input shaft 10.

Torque transfer from the input shaft 10 can be via the locking interface 26 or through the friction interface 28. Each side of a double activator 20a, 20b engages with a different floating gear 14a, 16a, 18a.

Any floating gear 14a, iSa, 18a may be fully locked to the input shaft 10 by its locking interface 26 (torque path A) and transmit full torque, or may be fully or partially locked to the input shaft 10 by its friction interface 28 torque (torque path B) and transmit full or partial torque.

The floating gears 14a, 16a, i8a need not be synchronous with the input shaft 10 but transmit torque through the friction interface 28 (torque path B) or the Iloating gears 14a, 16a, isa may be synchrcnous with the input shaft 10 and have either the locking interface 28, the friction interface 28 or both active, by different activators 20, 19, 22 but net transmitting any torque.

One advantage of the present invention is that friction interlaces 28 are always available, and avoids the requirement for a friction device (clutch) between the engine or motor of the vehicle and the transmission system.

The present invention provides that changing gear, changing from one gear ratio to another different gear ratio, can be achieved without interrupting the torque transmission (sometimes called a power shift") using the Iriction interfaces 28 of two or more different activators 20a, 20b, 19,22 on two or more different floating gears 14a, 16a, 18a. In a power shift the torque path from the input shaft 10 to the output shaft 12 changes from one gear to another with an uninterrupted torque transfer.

In order to change the gear ratio in use by the transmission system B from one to another the following exemplary method may be used.

The transmission system 8 is engaged with a third floating gear isa, the third floating gear 18a is in locking engagement with the second double activator 2Db, see Figure 5, that is the dog clutch is engaged between the third floating gear 1 Ba and second double activator 20b.

With the dog clutch engaged the friction clutch of the second single activator 22 is brought into engagement with the first floating gear 18a. The second double activator 20b then releases the third floating gear isa such that the third floating gear isa is engaged only by the friction clutch of the second single activator 22.

The friction interface 28 of the first double activator 20a is then brought into engagement with friction interface 28 of first floating gear i4a. Torque from the engine or motor is now being transmitted to the output shaft via the first floating gear 1 Ba. The speed of rotation of the input shaft is substantially unchanged, there will be relative movement or slip' between friction interface 28 of the first floating gear i4a and the friction interface 30 of the first double activator 20a. The relative movement or slip' will be reduced until the first floating gear 14a is synchronous with the input shaft 10, by further engaging the friction clutch by increasing the pressure between the friction interfaces 28, 30.

Once the first floating gear i4a is substantially synohronised with the input shaft 10, the locking interface 26 of the first single activator 19 is brought into locking engagement with the locking interlace of the first floating gear 14a. In some embodiments it is desirable to maintain a degree of slip, relative movement between the first floating gear 14a and the input shaft 10, in order ensure the teeth of the dog ring on the first floating gear 1 4a are received in recesses in the dog ring of the second single activator 19 and the teeth of the dog ring on the second single activator 19 are received in recesses in the dog ring of the first floating gear 14a.

The friction interlace 28 of the first double activator 20a is then disengaged from the friction interface 30 of the first floating gear 1 4a to complete the change in gear ratios.

It will be appreciated that since the friction interfaces and locking interfaces of each gear are controllable independently of one another alternative methods of changing gear ratios exist.

For example in the foregoing description ot the gear change or shift the step of frictionally engaging the outgoing gear, in the previous example this was the third floating gear 18a, with the friction interface 28 of the second single activator 22 may be omitted. In which case the friction interface 30 of the incoming gear, first floating gear 14a in the example above, will be engaged by the friction interface 28 of the first double activator 20a before the dog clutch or locking interfaces 25, 26 of the outgoing gear are disengaged.

Furthermore when transferring torque from one gear ratio to another it may be desirable to engage the friction interfaces 28, 30 between additional gear ratios, other than the incoming gear ratio and the outgoing gear ratio.

The transmission system 8 is efficient since the floating gears 14a, 16a, 18a can be maintained in engagement with the input shaft 10 without requiring require a continuous energy supply for example maintaining pressure or continuously applying force to the clutch plates as required by automatic transmission systems; this is achieved using the locking interfaces 25, 26. These locking interfaces 25, 26 rely upon the geometry of the locking device, dog clutch, to remain in the engaged position.

The transmission system 8 may be employed to provide a hill hold function by locking one floating gear 1 4a, 1 6a, 1 Ba with a locking interface 26 of an appropriate activator 20, 19, 22 and engaging another floating gear 14a, 16a, 1 Ba using the friction interface 28 with different activator 20, 19, 22.

Figure 6 illustrates a machine 110 for providing movement of the single activators 19,22 and double activators 20a, 20b.

The machine 110 comprises a piston 114 disposed within a cylinder or housing 112.

The housing 112 comprises a first chamber 116 and a second chamber 118, each taking a respective port 120, 122 for ingress and egress of a fluid.

A piston rod 115 is coupled to the piston 114; the piston rod 115 is mounted perpendicularly to the piston 114 and extends through an aperture in the housing 112.ln alternative embodiments other arrangements are envisaged for example the piston rod may be mounted collinearly with the piston and extend through an aperture in one of the end wall of the housing 112 rather than a side wall as illustrated. The housing 112 forms a double acting cylinder which can move the piston back and forth in a linear fashion by injecting pressurised fluid into a respective one of the tirst or second chambers 116, 118.

The piston comprises a first surface 124 having a first area dimension and a second surface 126 having a second area dimension. First area dimension is greater than second area dimension. Therefore when the pressure of the fluid applied to the first and second surfaces 124, 126 is the same, the force exerted in the direction indicated by direction arrow F is greater than that exerted in the direction indicated by direction arrow L. Preferably, the machine 110 is arranged such that the piston rod 115, when moved in the direction indicated by direction arrow F, engages the friction interface 28 of one of the single or double activators 20a, 2Db, 22 with the friction interface of one of the friction gears 14a, 16a, 18a. This is achieved by injecting fluid into first chamber 124 to apply pressure to first surface 124 whereby generating a force in the direction indicated by direction arrow F. The machine 110 can apply a greater force in the direction indicated by arrow F than in the direction indicated by direction arrow L. The machine 110 is preferably arranged such that when moving the piston rod 115 in the direction indicated by arrow L the single or double activator 19, 20a, 2Db engages the locking interface 25 of the respective activator 19, 20a, 2Db with a floating gear 14a, 16a, 18a. This has the advantage of being able to rapidly engage the locking interface 25 when moving in this direction for a given fluid flow rate, this is due to the smaller volume per unit length of the second chamber than the first chamber.

It is envisaged that a machine 110 will be coupled to the each of rods A, B and C in the transmission system 8 of Figure 5.

The machine 110 comprises a pair of valves 130, 132 coupled to the ports 120, 122 respectively by respective conduits or pipes. The valves ISO, 132 are illustrated in a de-energised condition. Valves 130, 132 are each coupled to fluid pressure source P such as a fluid pump and to a fluid reservoir or tank T. Valve 130 is preferably a solenoid valve comprising 3 ports and having 2 positions.

Valve 132 is preferably a solenoid valve comprising 3 ports and 3 positions.

Valve 130 comprises a first position 144 in which fluid may flow from the first chamber 116 via port 1 20 to the tank T. Fluid 110w from the pump P is blocked or prevented since the conduit from the pump P is terminated. Valve 130 comprises a second position 146 in which flow may flow or be pumped from the pump P into the first chamber 116, fluid flow to or from the tank I is blocked or prevented.

A spring or other suitable resilient device 140B biases the valve 130 to be in the first position 144. Valve 130 comprises a feedback loop 142 coupled between the first position 144 of the valve 130 and the conduit between the valve 130 and the port 120.

Valve 132 comprises a first position 148, in which the port 122 is fluidically coupled to the tank T, allowing fluid flow to/from the tank I. In the first position 148 fluid flow from the pump P is blocked or prevented by a termination. A spring or other resistant device 140 biases the valve 132 into the first position 148.

Valve 132 comprises a second position 150 in which fluid flow is prevented or blocked between the second chamber 118 and the tank I and fluid flow is blocked between the pump P and the second chamber 118.

Valve 132 comprises a third position 152 in which the pump P is coupled to the second chamber 118 and the conduit or fluidic path coupling the valve 132 to the Lank T is terminated or blocked.

In order to move the piston rod 115 in the direction indicated by direction arrow F, a force applied to the first surface 124 by the fluid in the first chamber 116 must be greater than a force applied to the second surface 126 by the fluid in the second chamber 118. This is achieved by activating the solenoid 138A to move the valve 130 into the second position 146, such that fluid may be pumped into the first chamber 116. The pressure created in the first chamber 116 forces the piston 114 in the direction indicated by arrow F fluid in the second chamber 118 is forced out through the valve 132, in the first position 148 and into the tank I. In order to stop the piston 114 moving in the direction indicated by arrow F, the valve 132 is activated to be in the second position 150 such that fluid flow into or out of the second chamber 118 is prevented, the motion of the piston 114 is stopped due to the resistance of the fluid in the second chamber 11310 being compressed by the piston 114.

In order to move the piston 114 in the direction indicated by arrow L a force on the second surface 126 exerted by fluid in the second chamber 118 must be greater than a force exerted on the first surface 124 by fluid in the first chamber 116, this is achieved by activating the sclenoid 138B on the second valve 132 so as to employ a third position 152, whereby coupling the pump P to the second chamber 118 and deactivating the solenoid 133A of the first valve 130, such that the first position 144 is employed whereby coupling the first chamber 116 to the tank T. Fluid can then be injected into the second chamber 118 by the pump P and ejected from the first chamber 116 by the movement of the piston 114; such that the piston 114 moves in the direction indicated by arrow L, that is to say, moving the first surface 124 towards the adjacent end wall of the housing 112.

In order to stop the piston 114 moving in the direction indicated by arrow L the first valve 130 activates the solenoid 1 38A to employ the second position 146 such that the pump P pumps fluid into the first chamber 116. Due to the greater area of the first surface 124 than that of the second surface 126; the force applied to the first surface 124 is greater than the force applied to the second surtace 126, whereby slowing and stopping movement ot the piston 114.

Optionally, the second valve 132 may be activated to employ the second or first positions 150, 148 to prevent fluid flow into the second chamber 118.

The first valve 130 controls the pressure of the fluid applied to the first chamber 116 and hence the first surface 124 of the piston 114. The second valve 132 controls the fluid flow to the second chamber 118.

In an alternative embodiment the piston 114 may be arranged such that the first surface 124 and second surface 126 have an equal area.

An advantage of the illustrated embodiment in which the area of the first surface 124 is greater than the area of the second surface 126 is that a fail-safe feature can be provided in event ot the valve failure. In the event of failure of first valvel3O the second valve 132 can move positioned in second position 150 whereby immobilising the piston 114. In the event of failure of second valve 132 valve for example second valve 132 is stuck in third position 152 in which fluid is injected into the second chamber 118 the first valve can be position in second position 146 in which fluid is injected into the first chamber 116, due to the fact that the area of first surface 124is greater than the area of second surface 126 the force applied by the fluid in the first chamber 116 in the direction indicated by direction arrow F is greater than the force applied to the second surface in the direction indicated by direction arrow L by the fluid in the second chamber 118.

Second valve 132 controls the flow rate of the fluid into and out of the second chamber 118; thereby the second valve 132 controls the speed and direction of movement of the piston 114 in both the F and L directions.

Valve 130 controls the pressure of the fluid applied to the first surface 124, and therefore when moving the piston 114 in the direction F the valve 130 controls the force applied to the friction interface 30 of the floating gear 1 4a, 1 Ga, 1 8a by the friction interface 28 of the single or double activator 19, 20a, 20b. By controlling the pressure applied to the first surface 114 the characteristics of a change or shift in gear ratios can be controlled. For example, if not enough pressure is applied then there will be relative movement between the friction interface 48 of the activator 19, 20a, 20b and the friction interface 30 of the floating gear 14a, iGa, 18a; in which case energy may be lost as heat due to friction between the friction interfaces 28, 30.

If too much pressure is applied too quickly then the transfer of torque onto incoming gear will be rapid, this may manifest as a jerk or jolt experience by the transmission system 8.

Turning now to Figures 7 and 8, there is illustrated a plot of the pressure/force versus the current of a typical hydraulic pressure valve. The pressure/force achieved for any given value of current applied to the solenoid is different depending upon whether the current is increasing or decreasing, this hysteresis problem can be substantial at lower values of current when trying to control smaller pressure values. The problem of hysteresis in the pressure valve can be overcome as shown in the embodiment of Figure 8.

In the embodiment of the activator 320a of Figure 8, the activator 320a comprises a locking interface 326 and a friction interface 328 which are mounted upon a body 329.

Body 329 is mounted on a support 360 in rolling or sliding contact to form a detent, for example by one or more balls 364, the balls 364 are mounted upon a spring or other resilient device 362 within the support 360, such that at least a portion of the baIls 364 can be received within the support 360 when the spring 362 is compressed. The balls 364 are biased against the body 329.

The body 329 comprises a recess or ramp 366 which engages with the balls 364 when moving the friction interfaces 328, 330 into engagement. The ramp 366 introduces a force which must be overcome when engaging the friction interface 328; this is due to the fact that the spring 362 must be compressed.

The ramp 366 is arranged such that when moving the body 329 to engage the friction interf ace 328 with the friction interface 330 the activator 320a and hence the machine 110 to which it is coupled must overcome the force exerted by the spring 362 upon the body 329.

This in turn requires the piston/cylinder machine 110 to exert sufficient force to overcome the spring force. In doing so, the piston 114 must apply a greater force/pressure to the activator 320a than it would otherwise need without the ramp 366 forcing the spring 362 into compression. This requires a greater pressure of fluid in the first chamber 116. In doing so, the pressure valve 130 operates at higher pressure values and requires greater current load.

This has the effect of operating the pressure valve 130 in the region 2 of the graph of Figure 7, where the hysteresis problem is reduced or eliminated.

The transmission system 8 preferably comprises a system for adaptively changing adaptive torque transfer function employed by the transmission system 8 to determine the requested pressure required between the friction interlaces 28, 30 to deliver a specified amount of torque. Each of the friction interfaces 28, 30 in the transmission system can be defined by a relationship or torque transfer function between the pressure between the friction interface 28 and friction interface 30 and the torque transferred through them.

The torque transfer function, the relationship between pressure and torque, is dependent upon many parameters of the transfer path and working conditions of the transmission system 8 for example the temperature, degree of slip or relative movement between the friction interface 28 and friction interface 30, the torque transfer function will be different for different friction interfaces 28, 30. The torque transfer function is also subject to change due to wear of the components during use.

Therefore embodiments of the present invention provide an adaptive or learning system for improving or maintaining the transmission systems performance. In particular to ensure that for a given pressure applied to between respective ones of the friction interfaces 28, 30 the torque transferred is substantially the same as expected by the system 8. Or alternatively that for a required degree of torque to be transferred the system 8 can apply the current amount of pressure between the function interfaces 28, 30.

In order to adapt or monitor the torque transfer function of a particular pair of friction interfaces 28, 30 it is desirable to know the force applied between the friction interfaces 28, and the amount of torque transferred for that force value. It may not be possible to measure the value of torque transferred between the friction interfaces 28, 30 or the force applied therebetween; however in many systems it may be possible to obtain a value indicative of the torque being delivered to the transmission system by the engine or motor and read the value of a control parameter controlling the force applied between the friction interfaces, for example a current value, or approximation thereto, of the current drawn by the pressure control valve 130. It is therefore desirable for any given value of torque delivered to the transmission system 8 to be able to update the control parameter value stored in a database of a control system (not shown) coupled to the transmission system B in order that the transmission system applies sufficient force between the frictions interfaces 28, 30 to optimise the transfer of torque between the first shaft 10 and the floating gears 1 4a, 1 6a, 1 Ba and hence through the transmission system 8.

The system 400, shown in Figure 10 can determine the torque transfer function of a given pair ot friction interfaces 28, 30 using the following procedure; Whilst operating the transmission system 8 in any given gear to be tested and preferably in stable conditions for example, motorway driving at constant speed.

The adaptive system 400 initiates a swap or change of the torque path. The transmission system B ceases using the locking interfaces 25, 26 to employ the friction interfaces 28, 30.

This is done by engaging the friction interfaces 28, 30 and subsequently disengaging the locking interfaces 25, 26. The force or pressure applied to the friction interfaces 28, 30 is preferably greater than that required to achieve the current torque value being transferred by the locking interfaces 25, 26.

The transmission system B then reduces the force or pressure applied to the friction interfaces 28, 30 by reducing force or pressure applied to the first interfaces 28, 30 by reducing the pressure applied to the first surface 124 of the piston 114 of the machine 110 by the fluid. The pressure of the fluid is reduced until the transmission system 8 experiences a predefined degree of slip, preferably a small degree of slip, micro slip'; for example until the rotational speed of shaft 10 is 5, 10, 15 rpm higher than the rotational speed of the floating gear 1 4a, 1 6a, 1 8a under test.

The adaptive system 400 receives or interrogates an engine/motor management system (not shown) controlling the engine or motor which is coupled to the transmission system 8 to obtain a value indicative of the torque being delivered by the engine or motor.

The adaptive system 400 has obtained a value indicative of the torque being transferred by the transmission system 8 and a value of a control parameter necessary for the transmission system 8 to achieve that torque capacity.

These values indicative of the torque and force or pressure can be compared to torque and values stored as a look up table, or other predelined torque transfer function of the transmission system 8, in a memory device. The adaptive system 400 can modify the torque transfer function or look up table values to incorporate the measured or recorded values.

Figure 9 illustrates a graph showing the adaption process. The upper axes 211 relate to the actions of the friction interfaces 28, 30 and the lower axes 210 relate to the actions of the locking interfaces 25, 26 of the gear under test. Line 214 indicates the changes to the pressure of the friction interfaces 28, 30. Line 216 reflects the position of the friction interface 28. Line 218 reflects the torque capacity through the friction interfaces 28, 30. Line 220 illustrates the degree of slip or relative movement between the friction interface 28 of the activator 19, 20a, 20b and friction interface 30 of the gear under test.

Line 222 illustrates the pressure applied to the locking interfaces 25, 26. Line 224 illustrates the position of the locking interface 25. Line 226 illustrates the degree of torque capacity through the locking interfaces 25, 26.

At time T0 the friction interfaces 28, 30 are disengaged and the locking interfaces 25, 26 are engaged with the floating gear 14a, 16a, 18a under test.

At time I1 the adaptive system 400 instructs the transmission system 8 to engage the friction interfaces 28, 30, pressure is applied by the machine 110, until a sufficient value exceeding that required to transfer the current torque being transferred to the floating gear 14a, 16a, 18a under test. This application of pressure or force to the friction interface 28 brings it into contact with the friction interface 30. In doing so, torque is transferred to the floating gear 1 4a, 1 Ga, 1 Ba under test via the friction interfaces 28, 30.

At time T2 the adaptive system 400 applies pressure to the locking interfaces 25 in order to disengage. This is to say the respective machine 110 coupled to the activator 20a, 20b, 22 which controls the floating gear 14a, 16a, 18a under test is moved in the direction indicated by direction arrow F by injecting pressurised fluid into the first chamber 116.

In doing so the locking interface 25 is disengaged from its position of interposition with the locking interface 26. The torque translerred to the floating gear 14a, 16a, iSa under test via the locking interfaces 25, 26 is reduced to zero.

At time T3 the adaptive system 400 reduces the pressure applied to the friction interfaces 28, 30. The friction interfaces 28, 30 then experience relative rotational movement with respect to each other.

This reduces the value of torque capacity. The transmission system 8 is held in this condition until time T5.

At time T4 the value 01 torque and pressure are recorded. Optionally at time T5, the adaptive system 400 may increases the pressure applied to the friction interfaces 28, 30 to eliminate the slip between them, and increasing the torque value translerred (not shown in the Figure)..

The adaptive system 400 instructs the transmissions system 8 to re-engage the locking interface 25 of the requisite activator 19, 20a, 2Gb with the locking interface 26 of the gear under test at time T6. Torque is now transferred to the floating gear 1 4a, 1 Ga, 1 Ba under test via the locking interfaces 25, 26.

At time 17 the adaptive system 400 instructs the transmission system 8 to reduce pressure to the friction interface 28. That is to say fluid under pressure is injected into the machine 110 controlling the respective activator 19, 20a, 2Gb activating the friction interface 28 of the floating gear 14a, 16a, 18a under test such that the machine 110 moves the piston in the direction indicated by direction arrow L. This is achieved by injecting the fluid into the second chamber 118 to apply force to the second surface 126.

This disengages the friction interface 28 from the friction interface 30. The torque transferred to the floating gear 1 4a, 1 6a, 1 8a under test is reduced to zero.

In some embodiments a direct measurement of the pressure value is not made, the current value drawn by the pressure valve 130 or other system component is used a measurement which is indicative of the pressure value.

It will be appreciated that when employed in a vehicle the adaptive system may instigate a measurement cycle at any time, preferably under steady state or stable conditions.

It will be appreciated that during the measurement cycle the vehicle may be requested; for example by the driver or other vehicle system to change the gear ratio. In such circumstances the transmission system would cease the measure cycle in progress and effect a change in gear ratio. Depending upon the timing of shift request within the measurement cycle the transmission system 8 may not need to disengage the locking interfaces 25, 26 of the current gear ratio before engaging the friction interfaces of the current gear. The transmission system 8 would shift the gear ratio by transferring the torque friction interface 28, 30 of the current, outgoing gear ratio of the incoming gear ratio.

Figure 10 illustrates a flow chart of the adaptive system 400 for monitoring and updating the torque transfer friction of any given pair of friction interfaces 28, 30.

Si. Detect stable conditions of operation, initiate measurement cycle of torque transfer function.

$2. Engage the friction interfaces 28, 30 of the current gear ratio in use, the gear under test.

53. Disengage the locking interfaces 25, 26 of the current gear ratio, gear under test.

S4. Reduce pressure applied to friction interfaces 28, 30 to introduce micro slip'.

S5. Wait until transmission system is in stable condition.

56. Measure, receive or record a torque value and a force or pressure value or alternatively a value indicative of the torque and a value indicative the force or pressure.

Si. Compare measured values of torque and pressure to stored values for measured friction interfaces. 58 follows if difference detected, otherwise S9 follows. In some embodiments SB may always follow S7 irrespective of whether or not the measured value and the stored values are the same or different.

SB. Update stored values with new measured values.

S9. Increase pressure between friction interfaces 28, 30 on gear ratio in use, gear under test.

Sb. Re-engage the locking interfaces using separate activator 19, 20a, 20b for the gear under test.

Sli. Disengage the friction interfaces 28, 30 on the gear under test.

It can be appreciated that various changes may be made within the scope of the present invention, for example, in other embodiments of the invention it is envisaged that the double activator may be provided with one friction interface on each side, alternatively the double activator may be provided with one locking interface on each side, the single activators may not be commanded together but independently each of each other. The floating gears may not be provided on the same shaft, some or all of the floating gears may be provided on the output shaft. A third shaft may be provided with floating gears which is also coupled to the output shaft.

The transmission system 8 may be provided with multiple output shafts each coupleable to the input shaft and to a further shaft or shafts which may be coupled to additional devices, such as in a vehicle application a differential and subsequently to the vehicles drive wheels.

The transmission system 8 may be provided with one or more additional clutches for coupling the input shaft to the engine or motor. These additional clutches may be employed only when launching the vehicle from a stationary position and/or during gear shifting events.

In some embodiments the transmission system may engage the friction interfaces between two or more gear ratios when launching the vehicle from a stationary position.

In alternative embodiments the cylinder/piston arrangement may be replaced with an alternative machine such as but not limited to a magnetic or electromagnetic device, a worm gear and electric motor, a pneumatic system or a manual system.

Claims

CLAIMS1. A transmission system comprising at least one floating gear rotationally mounted upon a first shaft, the system comprising a floating gear activation system for controlling torque transfer between the at least one floating gear and the first shaft, the gear activation system comprising a first device having a friction interface for frictional engagement with a friction interface disposed on a first side of the at least one floating gear, and a second device having a locking interface for an interpositional engagement with a locking interface disposed on a second side, opposing the first side, of the at least one floating gear, whereby the floating gear is rotationally coupleable to the first shaft by the friction interface and/or the locking interface.
2. The transmission system of claim 1 comprising at least one further gear mounted upon at least one further shaft said at least one further gear being coupled to a respective one of the at least one floating gear on the first shaft.
3. The transmission system of claim 2 wherein the at least one further gear is fixedly mounted on the second shaft for rotational movement therewith.
4. The transmission system of claim 2 wherein the at least one further gear is a floating gear rotationally mounted upon the second shaft.
5. The transmission system according to claim 1 wherein the friction interface comprises a clutching mechanism.
6. The transmission system according to claim 5 wherein the clutch mechanism is a cone clutch, preferably a multi plate cone clutch.
7. The transmission system according to claim 1 wherein the locking interface comprises a dog clutch.
8. The transmission system according to claim 1 wherein the first activator comprises a first and a second side, and the friction interface is provided on the first side and a locking interface is provided on the second side for engagement with a different floating gear provided on the first shaft.
9. The transmission system according to claim 1 wherein the first activator comprises a first and second side and the friction interface is provided on a first side and a second friction interface is provided on the second side for engaging with a different floating gear provided on the first shaft.
10. The transmission system according to claim 1 wherein the second activator comprises a first and second side and the locking interface is provided on a first side and a friction interface is provided on the second side for engaging with a different floating gear provided on the first shaft.
11. The transmission system according to claim 1 wherein the second activator comprises a first and second side and the locking interface is provided on a first side and a second looking interface is provided on the second side for engaging with a different floating gear provided on the first shaft.
12. A device for a transmission system comprising: a first side; a second side, opposing the first side; a friction interface for frictional engagement with a friction interface of a first gear; a locking interface for an interpositional engagement with a locking interface of a second gear; wherein the friction interface is disposed on the first side and the locking interlace is disposed on the second side.
13. A transmission system comprising the device of claim 12.
14. A vehicle comprising the transmission system of any of claims 1 to 11 or 13.
15. A method for activating a floating gear of a transmission system comprising: providing a first floating gear rotationally mounted upon a first shaft and a floating gear activation system for controlling torque transfer between the at least one floating gear and the first shaft, the gear activation system comprising a first device having a friction interface for frictional engagement with a friction interface disposed on a first side of the first floating gear, and a second device having a locking interface for an interpositional engagement with a locking interface disposed on a second side of the first floating gear, the second side opposing the first side; sliding the first device along the first shaft, in a first direction, into Irictional engagement with the Iriction interface on first side of the first gear, transferring torque to the first floating gear from the first shalt so as to substantially synchronise the first floating gear with the first shaft, and then sliding the second device along the first shaft, in a second direction opposing said first direction, into locking engagement with the locking interface on the second, opposing, side of the first gear, whereby locking the first floating gear with the first shaft.
16. The method for activating a floating gear of a transmission system according to claim comprising sliding the first device along the first shaft, in the second direction, so as to disengage the friction interface of the first device from the friction interface on the first side of the first gear.
17. A method for shifting gear ratios of a transmission system comprising: providing a first floating gear rotationally mounted upon a first shaft and a floating gear activation system for controlling torque transfer between the first floating gear and the first shalt, the gear activation system comprising a first device having a friction interface for frictional engagement with a friction interface disposed on a first side of the first floating gear, and a second device having a locking interface for interpositional engagement with a locking interface disposed on a second side of the first floating gear, the second side opposing the first side; providing a second floating gear rotationally mounted upon the first shaft and the gear activation system comprising a third device having a friction interface for frictional engagement with a friction interface disposed on a first side of the second floating gear, and a fourth device having a locking interface for interpositional engagement with a locking interface disposed on a second side of the second floating gear, the second side opposing the first side; engaging the friction interface of the first device with the friction interface of the first floating gear by sliding the first device along the first shaft; disengaging the locking interface of the second device from the locking interface of the first floating gear by sliding the second device along the first shaft; engaging the friction interface of the third device with the friction interface of the second floating gear by sliding the third device along the first shaft; disengaging the friction interface of the first device with the friction interface of the first floating gear by sliding the first device along the first shaft; engaging the locking interface of the fourth device with the locking interface of the second floating gear by sliding the fourth device along the first shaft.
18. The method for shifting gear ratios according to claim 17 wherein torque is transferred from the first floating gear to the second floating gear while the friction interface of the first device is engaged with the friction interface of the first floating gear and the friction interface of the third device is simultaneously engaged with the friction interface of the second floating gear, whereby effecting a powershift between the first floating gear and the second floating gear.
19. The method for shifting gear ratios according to either of claims 17 or 18 comprising providing at least one further floating gear mounted upon the first shaft, the or each at least one further floating gear having a friction interface for frictional engagement with a respective friction interface of at least one further device, the method further comprising; frictionally engaging one or more of the friction interfaces of the at least one further floating gears, and simultaneously, engaging the friction interface of the third device with the friction interface of the second floating gear by sliding the third device along the first shaft.
20. A method for holding a vehicle on a hill comprising: providing a first floating gear rotationally mounted upon a first shaft and a floating gear activation system for controlling torque transfer between the first floating gear and the first shaft, the gear activation system comprising a first device having a friction interface for frictional engagement with a friction interface disposed on a first side of the first floating gear, and a second device having a locking interface for interpositional engagement with a locking interface disposed on a second side of the first floating gear, the second side opposing the first side; providing at least one further floating gear mounted upon the first shaft, the or each at least one further floating gear having a friction interface for frictional engagement with a respective friction interface of at least one further device; wherein the method comprises; frictionally engaging the friction interface of the first floating gear with the first device and/or engaging the locking interface of the first floating with the second device; and simultaneously, engaging one or more of the friction interfaces of the at least one further floating gear with the respective friction interface of the at least one further device.
21. A method for shifting gear ratios of a transmission system comprising: providing a first floating gear rotationally mounted upon a first shaft and a floating gear activation system for controlling torque transfer between the first floating gear and the first shalt, the gear activation system comprising a first device having a friction interface for frictional engagement with a friction interface disposed on a first side of the first floating gear, and a second device having a locking interface for interpositional engagement with a locking interface disposed on a second side of the first floating gear, the second side opposing the first side; providing a second floating gear rotationally mounted upon a second shaft, the second floating gear being coupled to the first shaft by a further gear mounted on the first shalt and the gear activation system comprising a third device having a friction interface for frictional engagement with a friction interface disposed on a first side of the second floating gear, and a lourth device having a locking interface for interpositional engagement with a locking interface disposed on a second side of the second floating gear, the second side opposing the first side; engaging the Iriction interface of the first device with the friction interface of the lirst floating gear by sliding the first device along the first shaft; disengaging the locking interface of the second device from the locking interface of the first floating gear by sliding the second device along the first shaft; engaging the friction interface of the third device with the friction interface of the second floating gear by sliding the third device along the second shaft; disengaging the friction interface of the first device with the friction interface of the lirst floating gear by sliding the first device along the first shaft; engaging the locking interface of the fourth device with the locking interface of the second floating gear by sliding the fourth device along the second shaft.
22. A method for adapting the torque transfer lunction of a transmission system comprising: engaging a friction interface of first activator with a friction interface of the gear under test, disengaging a locking interface of a second activator from a locking interface of the gear under test; reducing the force applied by the friction interface of the first activator to the friction interface of the gear under test, whereby introducing a predefined degree of slip; recording a control parameter of the transmission system which produces the predefined degree of slip; receiving a parameter indicative of torque value delivered to the transmission system; interrogating a database to obtain a stored value of the control parameter corresponding to the value of the parameter indicative of torque value delivered to the transmission system; comparing the stored value of the control parameter with the recorded value of the control parameter; updating the data base with the recorded value of the control parameter if different to the stored values; increasing the pressure between the friction interface of the first activator and the friction interface of the gear under test so as to synchronise the gear under test with the shaft upon which it is mounted; engaging a locking interface of the gear under test by activating the second activator to interpose the locking interface of the second activator with the locking interface of the gear under test; disengaging the friction interface of the first activator from the friction interface of the gear under test.
23. The method of claim 22 comprising: detecting operation of the transmission system under stable conditions for a gear under test.
24. The method of either of claims 22 or 23 comprising: waiting until steady state conditions are reached with micro slip between the friction interfaces.
25. The method of any of claims 22 to 24 wherein the method omits the step of, interrogating the database to obtain a stored value of the control parameter corresponding to the value of the parameter indicative of torque value delivered to the transmission system; with the step of, calculating a value of the control parameter corresponding to the value of the parameter indicative of torque value delivered to the transmission system.
26. The method of any of claims 22 to 25 wherein the method replaces the step of, comparing the stored value of the control parameter with the recorded value of the control parameter and the method, updates the database with the recorded value of the control parameter irrespective of whether or not the value is different to the stored value.
27. The method of any of claims 22 to 26 wherein the method reduces the force applied by the friction interface ol the first activator to the friction interlace of the gear under test, to introduce a predefined degree ol micro-slip;
28. A mechanism for moving an activator in a transmission system, which mechanism comprises a double acting cylinder having a double ended piston, the cylinder having a lirst port for fluid action on a first end of the piston and a second port for fluid action on a second end of the piston, the first port coupled to a first pressure control valve such that the mechanism can control the pressure or force applied when moving the piston in a first direction for engaging a friction interface of a transmission system, and the second port coupled to a direction control valve, such that the mechanism can control the direction of travel of the piston within the cylinder.
29. A transmission system comprising a floating gear mounted upon a first shaft, the floating gear having a first side comprising a friction intertace and a second side comprising a locking interface, wherein a first activator is disposed adjacent the first side of the floating gear and comprises a Iriction interface for frictional engagement with the floating gear, a second activator being disposed on the second side of the floating gear and having a locking interface for interposition with the locking interface of the floating gear wherein the floating gear can be rotationally coupled to the first shaft by the first activator and/or the second activator.
30. A transmission system comprising a device slideably mounted upon a shaft, the device comprising first side comprising a friction interface for frictional engagement with a friction interface of a floating gear provided on the shaft wherein the device comprises a body mounted upon a support in rolling or sliding contact therewith for movement along the shaft, the device having a resilient device whose biasing force must be overcome when moving the body in a direction for engagement of the friction interface with the friction interface of the floating gear.
31. The transmission system according to claim 30 wherein the body comprises a ramp or recess which forms a detent for resisting movement of the body with respect to the support.
32. A transmission system substantially as described herein with reference to and/or as illustrated by the accompanying Figures.
33. A vehicle comprising a transmission substantially as described herein with reference to and/or as illustrated by the accompanying Figures.
34. An activator for a transmission system substantially as described herein with reference to and/or as illustrated by the accompanying Figures.
35. A method substantially as described herein with reference to and/or as illustrated by the accompanying Figures.