GB2448598A

GB2448598A - Magnetic coupling to flywheel

Info

Publication number: GB2448598A
Application number: GB0806939A
Authority: GB
Inventors: Jonathan C Wheals; Keith Ramsay; Andrew J Turner; Robert Robinson
Original assignee: Ricardo UK Ltd
Current assignee: Ricardo UK Ltd
Priority date: 2007-04-16
Filing date: 2008-04-16
Publication date: 2008-10-22
Also published as: GB0707280D0; GB0806939D0; WO2008125860A1

Abstract

A powertrain for a vehicle includes a flywheel 10 mounted in a vacuum or other isolation chamber 18. A magnetic coupling is used for selective connection to the flywheel 10. A first part of said magnetic coupling is located within the isolation chamber 18 and a second part is located outside the isolation chamber, thereby avoiding he need for a direct mechanical coupling, e.g. an input shaft, into the isolation chamber. The chamber 18 for the flywheel may be a vacuum chamber. The coupling is typically releasable by axial movement of an associated part along a splined connection 32 to weaken the magnetic field between opposing discs 22, 24 or concentric tubular portions of the coupling (50, 52 see fig 4).

Description

* . * 2448598 P717175GB-I Flywheel Arrangement for Motor Vehicles The

present invention relates to a flywheel arrangement for a vehicle powertrain. The invention also relates to an hybrid powertrain for a motor vehicle.

The emphasis on creating an environmentally-friendly impression for competitive motorsport, including Fl, has led to changes in competition regulations that previously prohibited certain types of energy storage devices, including those associated with hybrid powertrains.

Hybrid powertrains are attractive to the motorsport industry, not least because they are perceived to reduce fuel consumption, but also because they can be used to provide an overtaking boost to the power of the existing vehicle engine, thereby increasing spectator enjoyment.

A known form of hybrid powertrain uses propulsive force from an in-vacuum flywheel to supplement the power of the engine. However, there are difficulties in sealing the rotating shafts that extend into the vacuum chamber to couple the flywheel to the powertrain. It is also difficult to isolate the flywheel/vacuum chamber from the extreme torsional vibration and shocks that are associated with the irregularities of the track surface and minor contact or collisions that may occur between vehicles during a race.

It is an object of the invention to provide a flywheel arrangement which addresses one or more of the above problems.

According to one aspect of the invention, there is provided a hybrid powertrain for a vehicle which includes a CVT controlled in-vacuum flywheel, wherein torque is transferred to and/or from the flywheel using a magnetic coupling through a wall of the vacuum chamber.

According to another aspect of the invention, there is provided a hybrid powertrain for a vehicle which includes an in-vacuum flywheel in communication with a transmission, wherein the flywheel is mechanically isolated from the transmission by a magnetic coupling.

A further aspect of the invention provides a flywheel arrangement comprising a flywheel rotatably mounted in a vacuum chamber and a magnetic coupling arrangement for communication with said flywheel, e.g. for applying torque to the flywheel, through a wall of the vacuum chamber.

A still further aspect of the invention provides a vehicle drivetrain including a powertrain and a flywheel, wherein a magnetic coupling is arranged for transmitting torque between the powertrain and the flywheel.

A preferred magnetic coupling for use in the above aspects of the invention includes a first part coupled for rotation with an output shaft of a powertrain component and a second part coupled for rotation with said flywheel.

In a preferred embodiment, the flywheel is mounted in a vacuum chamber, wherein the magnetic coupling acts through a wall of said chamber, e.g. with first and second parts of the magnetic coupling arranged on opposite sides of the chamber wall.

A first part of the magnetic coupling may be movable relative to said second part in order to switch between a magnetically coupled state and a magnetically decoupled state. The switching movement of said first part is preferably controlled by a linear actuator. A controller may be included wherein the controller is preferably configured for regulating the switching movement of said first part, in order to induce a controlled slip of the magnetic coupling between said first and second parts.

The magnetic coupling may take various forms. For example, the coupling may include first and second axially opposed elements, e.g. rotatable discs, plates or bladed rotor elements. In other embodiments, the coupling may include concentric elements, e.g. concentric tubes.

The magnetic coupling is preferably arranged in communication with a CVT, wherein the CVI is also intended for communication between the vehicle engine and the vehicle driveline.

In each of the above aspects of the invention, it may be preferred to replace the vacuum chamber with another form of isolation chamber for said flywheel, e.g. a chamber containing a fluid, such as an air-helium mixture. In each case, the magnetic coupling is advantageous in that it obviates the need for a direct mechanical coupling with the flywheel, e.g. to obviate the need for a rotating shaft extending into the flywheel chamber and on which the flywheel is mounted or otherwise fixed for co-rotation.

The term flywheel when used in the statements of invention, description and claims of this specification is intended to cover all forms of rotatable kinetic energy storage device.

Other features and aspects of the invention will be readily apparent from the claims and the following description of preferred embodiments, made by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic view of an hybrid dnvetrain for a motor vehicle, incorporating a magnetic coupling between an in-vacuum flywheel and the vehicle engine and transmission; Figure 2 is similar to Figure 1 and shows a second embodiment of a magnetic coupling for the flywheel; Figure 3 is similar to Figures 1 and 2 and shows a third embodiment of a magnetic coupling for the flywheel; and Figure 4 is similar to Figures 1 to 3 and shows a fourth embodiment of a magnetic coupling for the flywheel and a method of suspending the vacuum chamber.

Figure 1 shows a flywheel arrangement, wherein a flywheel 10 is fixedly mounted on a shaft 12, the latter being rotatable in bearings 14, 16. The flywheel 10, shaft 12 and bearings 14, 16 are enclosed in a vacuum chamber 18 having a front wall 20.

A magnetic coupling is provided for transmitting torque through the front wall 20 of the vacuum chamber 18. In this embodiment, the magnetic coupling consists of a pair of opposing discs 22, 24 of the same kind and configuration. Each disc 22, 24 includes a pair of permanent magnets 26, 28 of opposing polarity, the magnets 26, 28 being mounted on one face of the disc 22, 24. The discs 22, 24 are coaxial with the flywheel and shaft 12.

A first disc 22 of the magnetic coupling is mounted in the vacuum chamber 18 at one end of the shaft 12, for rotation therewith. The disc 22 is arranged with its magnets 26, 28 adjacent the front wall 20 of the vacuum chamber 18.

The second disc 24 of the magnetic coupling is mounted at the end of a separate rotatable shaft 30, outside the vacuum chamber 18. The second disc 24 is axially reciprocable relative to the vacuum chamber 18, i.e. left to right and vice versa as viewed in Figure 1, by virtue of a splined coupling 32 between the shaft 30 and a transmission, which in this embodiment is a continuously variable transmission or CVT 34. Axial movement of the shaft 30 and hence the second disc 24 is facilitated by a linear actuator 36, preferably an hydraulic piston. The actuator 36 is controlled by the vehicle ECU, indicated at 38.

In the present embodiment of the powertrain, the CVT 34 is arranged in selective communication with a clutch 40. The clutch 40 provides communication between the CVT 34 and the vehicle driveline, indicated generally at 42, the latter being arranged in communication with the vehicle wheels 44. The CVT 34 and clutch 40 are controlled by the ECU 38. The vehicle engine is not shown and its position is not critical to the invention.

The flywheel 10 is intended to act as a kinetic energy Store for the vehicle. Stored energy can then be used to supplement the drive force transmitted to the vehicle wheels 44 by the vehicle driveline 42. In one example, the ECU can be programmed to charge the flywheel 10 during vehicle braking, and to discharge stored energy from the flywheel to the drive train during acceleration. However, the flywheel 10 can also be used to decelerate the vehicle. A control device can be used to vary the energy flow to/from the flywheel 10 according to vehicle operating conditions.

Torque can be transmitted to or from the flywheel 10 by movement of the outer disc 24 towards the inner disc 22. As the magnets 26, 28 on the outer disc 24 are brought into close proximity with the magnets on the inner disc 22, a magnetic alignment of the discs 22, 24 takes place, whereby the two discs 22, 24 become magnetically coupled so as to be rotatable together. Hence, the transmission 34 and flywheel 10 become effectively connected to one another, via the magnetic attraction between the two discs 22, 24.

The arrangement is advantageous in that torque can be transmitted through the wall 20 of the vacuum chamber 18, without the need for a mechanical connection or linkage through the wall 20 of the vacuum chamber 18, thereby obviating the need for complex seal arrangements for shafts that would otherwise extend into the vacuum chamber 18.

It will be understood that the magnetic coupling between the discs 22, 24 can be disconnected by movement of the second disc 24 to the left as viewed in Figure 1.

Hence, the disc 24 on the outside of the chamber 18 acts as a clutch between the flywheel 10 and the CVT 34.

The magnetic coupling can be configured to slip at a predetermined torque value, so as to prevent overload to the flywheel 10. Alternatively or additionally, the ECU can be programmed to disconnect the magnetic coupling at predetermined thresholds.

The magnetic coupling that occurs between the discs 22, 24 may generate axial loads within the arrangement, resulting in bearing losses and the transmission of undesired vibration to the flywheel 10. To minimise the effect of such axial loads, permanent magnets 46 of corresponding polarity are provided in a spaced array on the opposite side of the flywheel 10 from first disc 22. The repulsion between the magnets 46, 48 serves to counteract axial loads which are generated as the two discs 22, 24 become magnetically coupled. In this embodiment, a first magnet 46 is mounted on a rear wall 48 of the vacuum chamber 18 and a second magnet 46 is mounted on one of the bearings 16 for the flywheel 10.

Figure 2 shows a powertrain which is substantially the same as the arrangement described above. However, in this embodiment the counteracting magnets 46, 48 are provided on the opposite side of the flywheel 10 to those shown in Figure 1. More particularly, the magnets 46 are arranged on opposing faces of the discs 22, 24.

Figure 3 shows a further powertrain, wherein the need for counteracting magnets of the kind shown in Figures 1 and 2 is obviated, by using two magnetic couplings, one on either side of the vacuum chamber 18. Each coupling is identical and has its own splined connection 32 and linear actuator 36. Hence, the ECU 38 can bring about simultaneous movement of the discs 24 on the exterior of the vacuum chamber 18, so that equal and opposite axial loads are generated by the two magnetic couplings. As well as reducing bearing losses and deleterious effects on the flywheel 10, the use of dual couplings increases the torque capacity of the arrangement.

The above embodiments have been described with reference to magnetic couplings using pairs of opposing permanent magnets mounted on rotatable discs. It will be understood that single magnets or multiple pairs can be used on each disc. Other magnetic arrangements and materials may be used in addition or as alternatives, for example ferrous elements as opposed to permanent magnets or an electro magnetic arrangement which acts through a wall of the vacuum chamber.

An alternative magnetic coupling is shown in Figure 4, wherein the flywheel shaft 12 is coupled to a tubular magnet 50 (shown in cross section) on the inside of the vacuum chamber 18. A tubular magnet 52 (again shown in cross section) of smaller diameter is provided on the outside of the vacuum chamber 18. The front wall 20 of the vacuum chamber 18 defines a recess within the inner' tubular magnet 50, and the arrangement is such that the outer' tubular magnet 52 can be moved axially (via an actuator and splined connection, not shown) into or out of said recess, in order to bring about magnetic coupling/decoupling. The concentric magnetic coupling shown in Figure 4 generates less of an axial load than the parallel plate couplings shown in Figures 1 to 3.

Nevertheless, it may be preferred to include a counteracting arrangement, for example the spaced magnets 46 in Figure 1.

The magnetic couplings described above are advantageous in that they obviate the need for a rigid connection to the flywheel 10 through the walls of the vacuum chamber 18.

Hence, the vacuum chamber 18 can be resiliently suspended, for example using spring dampers 564 as shown in Figure 4 or using magneto-rheological fluids controlled by ECU strategy, so as to further isolate the flywheel from torsional vibrations associated with use of the vehicle.

Gear elements may be located within the vacuum chamber to further reduce losses, e.g. magnetic-type reduction devices.

It may be preferred to replace the vacuum chambers referred to herein with another form of isolation chamber for said flywheel, e.g. a chamber containing a gas such as helium. In each case, the magnetic coupling is advantageous in that it obviates the need for a direct mechanical coupling with the flywheel, e.g. a shaft extending into the flywheel chamber.

Claims

Claims 1. A hybrid powertrain for a vehicle comprising a transmission

in communication with a flywheel via a magnetic coupling that can be selectively engaged to charge or discharge energy from the flywheel
2. A hybrid powertrain according to claim I wherein the flywheel is mechanically isolated from the powertrain.
3. A hybrid powertrain according to claim I or claim 2 wherein the flywheel is mounted in an isolation chamber, such as a vacuum chamber, wherein the magnetic coupling acts through a wall of said chamber.
4. A hybrid powertrain according to claim 3 wherein the magnetic coupling includes first and second parts arranged on opposite sides of the chamber wall.
5. A hybrid powertrain according to any preceding claim wherein the magnetic coupling includes a first part coupled for rotation with an output shaft of a powertrain component and a second part coupled for rotation with said flywheel.
6. A hybrid powerirain according to claim 4 or claim 5 wherein said first part is movable relative to said second part in order to switch between a magnetically coupled state and a magnetically decoupled state.
7. A hybrid powertrain according to claim 6 wherein the switching movement of said first part is controlled by a linear actuator.
8. A hybrid powertrain according to claim 6 or claim 7, including a controller configured for regulating the switching movement of said first part, in order to induce slip of the magnetic coupling between said first arid second parts.
9. A hybrid powertrain according to any preceding claim wherein the magnetic coupling is in the form of a) first and second axially opposed elements, e.g. rotatable discs, plates or bladed rotor elements, or b) concentric elements, e.g. concentric tubes.
10. A hybrid powertrain according to any of claims 4 to 9 wherein said first part is arranged in communication with a CVT.
11. A flywheel arrangement for a vehicle powertrain comprising a flywheel rotatably mounted in a vacuum chamber and a magnetic coupling arrangement for applying torque to and/or from the flywheel through a wall of the vacuum chamber.
12. A flywheel arrangement according to claim 11, wherein the magnetic coupling includes a first part within the vacuum chamber and second part outside the vacuum chamber.
13. A flywheel arrangement according to claim 12, wherein the second part is selectively movable relative to said first part to bring about a magnetic connection between said first and second parts.
14. A flywheel arrangement according to claim 13, wherein the second part is movable under control of a linear actuator.
15. A flywheel arrangement according to claim 13, wherein the second part is arranged in communication with a CVT.
16. A flywheel according to any of claims 12 to 15, wherein the first part is fixed for rotation with the flywheel.
17. A flywheel arrangement according to any of claims 11 to 16, wherein the flywheel is mounted on a rotatable shaft which is contained within the vacuum chamber and wherein the magnetic coupling is arranged to transmit torque to or from the flywheel via said shaft.
18. A flywheel arrangement according to any of claims 11 to 17, wherein the magnetic coupling comprises a pair of opposing rotor elements, e.g. plates, discs or bladed rotor elements, one inside the vacuum chamber and the other outside the vacuum chamber.
19. A flywheel arrangement according to any of claims 11 to 18, wherein the arrangement includes a magnetic array configured to reduce the effect of axial loads generated by the magnetic coupling, in use.
20. A flywheel arrangement according to claim 19, wherein the magnetic array comprises a pair of spaced magnets of corresponding polarity arranged to repel one another in the event of an axial load being generated by the magnetic coupling.
21. A flywheel arrangement according to any of claims 11 to 20, wherein the arrangement includes a first magnetic coupling on one side of the flywheel and a second magnetic coupling on another side of the flywheel, each magnetic coupling being arranged to transmit torque through a respective wall of the vacuum chamber.
22. A flywheel arrangement according to claim 21, wherein the first and second magnetic couplings are arranged for simultaneous actuation.
23. A flywheel according to any of claims 11 to 17 or 19 to 22, wherein the magnetic coupling comprises a pair of concentric tubes.
24. A flywheel arrangement according to any of claims 11 to 23, wherein the vacuum chamber is mounted on vibration damping means.
25. A flywheel arrangement according to claim 24, wherein the vibration damping means comprises spring dampers and/or a magneto-rheotogical fluid system.
26. A hybrid powerirain for a motor vehicle comprising a flywheel arrangement according to any of claims 11 to 25.
27. A hybrid powertrain for a vehicle comprising a transmission in communication with an in-vacuum flywheel, wherein the flywheel is mechanically isolated from the vehicle transmission by a magnetic coupling that can be selectively engaged to charge or discharge energy from the flywheel.
28. A hybrid powertrain for a vehicle comprising a CVT controlled flywheel mounted in an isolation chamber wherein torque is transferred to and/or from the flywheel using a magnetic coupling through a wall of the isolation chamber.
29. A flywheel arrangement substantially as described and illustrated in any of the Figures herein.
30. A hybrid powertrain substantially as described and illustrated in any of the Figures herein.