GB2410300A

GB2410300A - A rotating motion energy converter

Info

Publication number: GB2410300A
Application number: GB0404548A
Authority: GB
Inventors: Thomas Tsoi Hei Ma
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-01-22
Filing date: 2004-03-01
Publication date: 2005-07-27
Anticipated expiration: 2024-03-01
Also published as: GB0404548D0; GB2410300B; GB0401600D0; GB0401339D0

Abstract

A rotating motion energy converter comprises a gyroscopic energy conversion module 20 driven by a rotating shaft 84. The module comprises a circular housing 22 with an internal ring track or groove 21, a moveable frame 30 supported resiliently by a flexible flange 26 and flexible seals 31 revolving about an axis 32, and a spinning rotor 40 supported within the revolving frame to rotate about another axis 42. An electric generator 44 is driven by the spinning rotor. The module is mounted for rotation about the rotating shaft but set at an offset angle causing the device to wobble about the shaft axis. The module also comprises an electric motor 46 for driving the rotor at times when it is not gaining rotational energy from the rotating shaft. The revolving frame is constrained in rotation within the housing of the module by a one-to-one ratio epicyclic gear set 35, 37 and connected to the revolving frame by an extension shaft 34.

Description

24 1 0300 - 1 -

ROTATING MOTION ENERGY CONVERTER

Field of the invention

The present invention relates to a device for converting low frequency rotating motion to electricity. In particular it relates to a device for converting the energy collected by a wind or marine turbine to electricity.

lo Background of the invention

Most developments of wind and marine power have concentrated on the conversion of the energy in the wind or current into a form which can be converted to electrical energy by conventional high speed rotary generators.

Typical systems employ high ratio gearbox or hydraulic power system to convert low speed rotating motion (below 60 rpm) to high speed rotation (1500 to 3000 rpm) suitable for the generator running at an air-gap velocity of typically 50 m/s or higher. This mechanical interface required for speed conversion is the most complicated and costly part of a wind or marine energy converter. In addition, hydraulic systems contribute to energy losses and require regular maintenance.

Summary of the invention

In order to mitigate at least some of the above problems, there is provided in the present invention an energy conversion module driven by a rotating shaft, the module comprising a circular housing with an internal ring track or groove, a moveable frame supported resiliently within the housing to revolve about a first axis substantially concentric with the said ring track, a spinning rotor supported within the said revolving frame to rotate about a second axis which is perpendicular to the said first axis of the revolving frame and which lies in the same plane as the said ring track in the housing such that - 2 the spindle of the spinning rotor engages loosely at both ends within the said ring track while revolving with the said revolving frame around the ring track, and an electric generator driven by the said spinning rotor for converting the rotational energy of the rotor to electricity, characterized in that the module is mounted for rotation about the rotating shaft axis with the first axis of the said revolving frame subtending an angle with the rotating shaft axis thus causing the first axis to wobble about the lo rotating shaft axis and inducing the spinning rotor into precession motion around the said first axis while the module is driven by the rotating shaft, and that the said revolving frame is constrained in rotation within the said housing of the module by a one-to-one ratio epicyclic gear set disposed between the said subtended angle, the gear set having a sun gear mounted to a fixed datum concentric with the rotating shaft axis and a planetary gear engaged for rotation around the sun gear and mounted concentric with first axis of the revolving frame for it to drive the frame to revolve relative to the said housing at the same frequency as the first axis is wobbled around the sun gear, and further characterized in that the phasing of the said revolution of the frame relative to the said wobbling of the first axis is positioned by the said epicyclic gear set such that the said spinning rotor gains rotational energy by synchronized transfer of angular momentum from the periodic wobbling motion of the first axis of the resiliently supported revolving frame which is the precession axis of the spinning rotor forcing the spindle of the spinning rotor to tilt by gyroscopic action into continuous rolling contact with the side walls of the ring track thus driving the rotor while revolving in precession motion around the ring track.

In the invention, the spinning rotor in the energy conversion module is set into wobbling motion by the rotating shaft in such a way that the induced gyroscopic precession of the rotor is converted to rotational energy transferred synchronously to the spinning rotor. This converts, in one step, low speed rotating motion of the rotating shaft to high speed spinning of the rotor suitable for power generation using a generator of small size and high efficiency driven at high speed by the rotor.

The invention may therefore be used advantageously driven at low speed by a wind or marine turbine. Compared with other known wind and marine energy converters, the lo invention does not rely on intermediate mechanical interface for speed conversion, therefore has low cost and low energy loss, and can be completely sealed and maintenance free.

In the invention, by mechanically coupling the wobbling of the spinning rotor at the same frequency and in the correct phase with the precession of the spinning rotor, no additional control system is necessary for achieving synchronized transfer of rotational energy to the spinning rotor, which will happen automatically by design.

In the invention, for a substantially constant designed speed of the rotating shaft, the said subtended angle between the said first axis of the revolving frame and the said rotating shaft axis is predetermined such that the precession speed of the spinning rotor induced by the wobbling rate of the spinning rotor through the said subtended angle is substantially the same as the rotating speed of the rotating shaft. In this case, the epicyclic gear set will only need to transfer power by relatively small amounts to influence the precession of the spinning rotor to achieve matching in speed for synchronization.

Such arrangement is suitable for application in a wind or marine turbine where the turbine is maintained at a constant speed by controlling the pitch of the turbine blades while operating in different wind or current speeds. - 4 -

Additionally, the said sun gear of the epicyclic gear set is preferably rotatable by an actuator for varying the phasing of the precession relative to the wobbling of the spinning rotor in order to optimise the phasing for synchronization.

The said energy conversion module further comprises an electric motor for driving the rotor at times when the rotor is not gaining rotational energy from the rotating shaft lo For compactness, this may be integrated with the said electric generator into a combined generator/motor unit.

The invention makes use of a known principle of a gyroscopic device described in Patent US3726146 and marketed under the trade name PowerballrM. This is a body-building ball for hand and wrist exercise composed of gyro ball mounted on ring track. In use, under swinging of the hand, the rotation speed of the gyro ball can be increased from hundreds of RPM to thousands of RPM, resulting in a great force exerted on the hand. When applied correctly, the swinging frequency of the hand (which is variable and adjusted adaptively by feel to the precession by the user) would be synchronized with the precession frequency.

In the present invention using a parallel principle in the energy conversion module, the precession frequency of the spinning rotor is always matched by mechanical coupling to the wobbling frequency ensuring synchronization, and the rotational energy transferred to the rotor will be converted to electricity by the generator. Of course, the phasing of the precession relative to the wobbling must be correctly positioned in order to ensure smooth and efficient transfer of rotational energy to the rotor.

The invention differs from other known gyro-based energy conversion devices such as those described in Patents GB2058938 and US4300871, where the method of energy conversion relies on capturing the reactive movements of the precession frame by connecting the frame to a reciprocating piston pump operated at low speed, and the pumped fluid is used to power a hydraulic motor to drive a rotary generator at high speed. As explained earlier, such mechanical interface for speed conversion is complicated and costly.

Also the hydraulic system contributes to energy losses and require regular maintenance. All these problems are mitigated by the present invention.

Preferably, a controller is provided for varying the electrical load on the generator according to the energy available from the rotor such that there is sufficient residual rotational energy in the rotor to sustain the spinning of the rotor for an indefinite period against bearing and windage losses. To reduce such losses, the energy conversion module may be housed within a sealed chamber which is evacuated of air.

Brief description of the drawing

The invention will now be described further by way of example with reference to the accompanying drawings in which Figure 1 shows a schematic cross-sectional view of a preferred embodiment of the energy conversion module driven by a rotating shaft, and Figure 2 shows a controller for regulating the energy transfer within the energy conversion module of Figure 1.

Detailed description of the preferred embodiment

Figure 1 shows an energy conversion module 20 driven by a rotating shaft 84. The module 20 comprises a circular housing 22 with an internal ring track or groove 21, a moveable frame 30 supported resiliently by flexible flange 26 and flexible seals 31 within the housing 22 to revolve - 6 about a first axis 32 substantially concentric with the ring track 21, a spinning rotor 40 supported within the revolving frame 30 to rotate about a second axis 32 which is perpendicular to the first axis 32 of the revolving frame 30 and which lies in the same plane as the ring track 21 in the housing 22 such that the spindle 41 of the spinning rotor 40 engages loosely at both ends within the ring track 21 while revolving with the revolving frame 30 around the ring track 21, and an electric generator 44 driven by the spinning lo rotor 40 for converting the rotational energy of the rotor to electricity. In the invention, the module 20 is mounted within a shaft casing 82 fixed to the rotating shaft 84 with the first axis 32 of the revolving frame 30 subtending an angle with the rotating shaft axis 84 thus causing the first axis 32 to wobble about the rotating shaft axis 84 and inducing the spinning rotor 40 into precession motion around the first axis 32 while the module 20 is driven by the rotating shaft 84. The revolving frame 30 is constrained in rotation within the housing 22 of the module 20 by a one-to one ratio epicyclic gear set 35, 37 disposed between the said subtended angle and connected by an extension shaft 34 to the revolving frame 30. The gear set has a sun gear 37 mounted to a fixed datum concentric with the rotating shaft axis 84 and a planetary gear 35 engaged for rotation around the sun gear 37 and mounted to the shaft 34 of the revolving frame 30 for it to drive the frame 30 to revolve relative to the housing 22 at the same frequency as the first axis 32 is wobbled around the sun gear 37. Finally, the phasing of the revolution of the frame 30 relative to the wobbling of the first axis 32 is positioned by the epicyclic gear set 35, 37 such that the spinning rotor 40 gains rotational energy by synchronized transfer of angular momentum from the periodic wobbling motion against the flexible seals 31 of the first axis 32 of the resiliently supported revolving frame 30 which is the precession axis of the spinning rotor 40 forcing the spindle 41 of the spinning rotor 40 to tilt by gyroscopic action into continuous rolling contact with the - 7 side walls of the ring track 21 thus driving the rotor 40 while revolving in precession motion around the ring track.

It would be clear from the above that the ratio of rotor speed versus precession speed is fixed when the spindle 41 is forced into rolling contact with the ring track 21, and is determined by the diameter ratio of the ring track 21 and the spindle 41. Thus, the energy conversion module 20 serves as a speed conversion device lo having a very high step- up ratio and high efficiency provided that there is no slip at the rolling contact.

In Figure 1, the spinning rotor 40 in the energy conversion module 20 installed within the shaft casing 82 is set into wobbling motion by the rotating shaft 84 in such a way that the induced gyroscopic precession of the rotor 40 is converted to rotational energy transferred synchronously to the spinning rotor 40. This converts, in one step, low speed rotating motion of the rotating shaft 84 to high speed spinning of the rotor 40 suitable for power generation using a generator 44 of small size and high efficiency driven at high speed by the rotor 40.

The invention may therefore be used advantageously driven at low speed by a wind or marine turbine 80 as shown in Figure 1. Compared with other known wind and marine energy converters, the invention does not rely on intermediate mechanical interface for speed conversion, therefore has low cost and low energy loss, and can be completely sealed and maintenance free.

In the invention, by mechanically coupling the wobbling of the spinning rotor 40 at the same frequency and in the correct phase with the precession of the spinning rotor 40, no additional control system is necessary for achieving synchronized transfer of rotational energy to the spinning rotor, which will happen automatically by design. - 8 -

In Figure 1, for a substantially constant designed speed of the rotating shaft 84, the said subtended angle between the first axis 32 of the revolving frame 30 and the rotating shaft axis 84 is predetermined such that the precession speed of the spinning rotor 40 induced by the wobbling rate of the spinning rotor 40 through the said subtended angle is substantially the same as the rotating speed of the rotating shaft 84. In this case, the epicyclic gear set 35, 37 will only need to transfer power by lo relatively small amounts to influence the precession to achieve matching in speed for synchronization. This reduces the size and torque capacity of the extension shaft 34 and the epicyclic gear set 35, 37 since most of the power transfer will come by gyroscopic action induced directly by the rotating shaft 84. Such arrangement is suitable for application in a wind or marine turbine as shown in Figure 1 where the turbine 80 is maintained at constant speed by controlling the pitch of the turbine blades while operating in different wind or current speeds.

Additionally in Figure 1, the sun gear 37 of the epicyclic gear set is rotatable by an actuator (not shown) for varying the phasing of the precession relative to the wobbling of the rotor 40 in order to optimise the phasing for synchronization.

In Figure 1, the energy conversion module 20 further comprises an electric motor 46 for driving the rotor 40 at times when the rotor is not gaining rotational energy from the rotating shaft 84. For compactness, this may be integrated with the electric generator 44 into a combined generator/motor unit, which could be one or both of the units 44 and 46.

Figure 2 shows a torque sensor 38 which measures the power transfer through the extension shaft 34 to the epicyclic gear set 35, 37. Another sensor 48 measures the - 9 - spinning speed of the rotor 40. Signals from one or both sensors 38, 48 are fed to a controller 28 which varies the electrical load on the generator 44 according to the energy available from the rotor 40 such that there is sufficient residual rotational energy in the rotor 40 to sustain the spinning of the rotor against bearing and windage losses.

To reduce such losses, the housing 22 may be sealed and evacuated of air.

0 In Figure 2, if the electric load is in balance with power input by gyroscopic action from the rotating shaft, no torque will pass through the extension shaft 34 to the epicyclic gear set 35, 37. On the other hand, any unbalance will result in torque transmitted into or out of the energy conversion module 20 along the extension shaft 34 which will be sensed by the sensor 38.

In Figure 2, the controller 28 also controls a rotating actuator 39 for adjusting the sun gear 37 in order to vary the phasing between the precession and the wobbling of the spinning rotor, optimised using signals from sensors 38, 48.

The motor 46 is required to drive the rotor 40 up to a minimum speed for the gyro effect to take hold, after which the rotor speed could be selfsustaining by regulating the generator 44 alone. If the rotating shaft 84 stops turning, the rotor 40 will slow down or stop, then it must be spun up using the motor 46 when the rotating shaft is turning again.

In Figure 2, the generator 44 feeds electricity into an external power grid 24 connected to the energy conversion module 20 via the controller 28 and sliding contacts (not shown) between the revolving frame 30 and the housing 22.

The same grid 24 may supply electric power to the motor 46 when required. Alternatively, the generator 44 may be used to charge an on-board battery (not shown) which then supplies the motor 46 when required. -

Claims

1. An energy conversion module driven by a rotating shaft, the module comprising a circular housing with an internal ring track or groove, a moveable frame supported resiliently within the housing to revolve about a first axis substantially concentric with the said ring track, a spinning rotor supported within the said revolving frame to rotate about a second axis which is perpendicular to the lo said first axis of the revolving frame and which lies in the same plane as the said ring track in the housing such that the spindle of the spinning rotor engages loosely at both ends within the said ring track while revolving with the said revolving frame around the ring track, and an electric generator driven by the said spinning rotor for converting the rotational energy of the rotor to electricity, characterized in that the module is mounted for rotation about the rotating shaft axis with the first axis of the said revolving frame subtending an angle with the rotating shaft axis thus causing the first axis to wobble about the rotating shaft axis and inducing the spinning rotor into precession motion around the said first axis while the module is driven by the rotating shaft, and that the said revolving frame is constrained in rotation within the said housing of the module by a one-to-one ratio epicyclic gear set disposed between the said subtended angle, the gear set having a sun gear mounted to a fixed datum concentric with the rotating shaft axis and a planetary gear engaged for rotation around the sun gear and mounted concentric with first axis of the revolving frame for it to drive the frame to revolve relative to the said housing at the same frequency as the first axis is wobbled around the sun gear, and further characterized in that the phasing of the said revolution of the frame relative to the said wobbling of the first axis is positioned by the said epicyclic gear set such that the said spinning rotor gains rotational energy by synchronized transfer of angular momentum from the periodic wobbling motion of the first axis of the resiliently supported revolving frame which is the precession axis of the spinning rotor forcing the spindle of the spinning rotor to tilt by gyroscopic action into continuous rolling contact with the side walls of the ring track thus driving the rotor while revolving in precession motion around the ring track.

2. An energy conversion module driven by a rotating shaft as claimed in claim 1, wherein for a substantially lo constant designed speed of the rotating shaft, the said subtended angle between the said first axis of the revolving frame and the said rotating shaft axis is predetermined such that the precession speed of the spinning rotor induced by the wobbling rate of the spinning rotor through the said subtended angle is substantially the same as the rotating speed of the rotating shaft, thus requiring the said epicyclic gear set to transfer power by relatively small amounts to influence the precession to achieve matching in speed for synchronization.

3. An energy conversion module driven by a rotating shaft as claimed in claim 1 or 2, wherein the said sun gear of the epicycle gear set is rotatable by an actuator for varying the phasing of the precession relative to the wobbling of the spinning rotor in order to optimise the phasing for synchronization.

4. An energy conversion module driven by a rotating shaft as claimed in claims 1, wherein said energy conversion module further comprises an electric motor for driving the rotor at times when the rotor is not gaining rotational energy from the rotating shaft.

5. An energy conversion module driven by a rotating shaft as claimed in claims 1 and 4, wherein the said electric generator and electric motor are integrated into one or more combined generator/motor units.

- 12 -

6. An energy conversion module driven by a rotating shaft as claimed in any preceding claim, wherein a controller is provided for varying the electrical load on the said generator according to the energy available from the rotor such that there is sufficient residual rotational energy in the rotor to sustain the spinning of the rotor against bearing and windage losses.

7. An energy conversion module driven by a rotating lo shaft as claimed in claim 6, wherein a torque sensor is provided for measuring the power transfer through the said epicyclic gear set and the resulting signal is used by the controller for varying the electrical load on the said generator.

8. An energy conversion module driven by a rotating shaft as claimed in claims 3 and 6, wherein the controller also controls the said actuator for turning the sun gear in order to vary the phasing between the precession and the wobbling of the spinning rotor.

9. An energy conversion module driven by a rotating shaft as claimed in any preceding claim, wherein the rotating shaft is driven at a substantially constant speed by a wind or marine turbine.