Such an assembly is generally known in the art. In wind turbines the mechanical power is made available via a slowly rotating shaft which is connected to the hub and the blades of the wind turbine. A speed of revolution of approximately 10-30 revolutions per minute is mentioned by way of example. This speed of revolution is too low to generate electrical energy efficiently with the aid of a conventional generator. In order to solve this problem, in the prior art the speed of revolution is increased with the aid of a gearbox transmission.

In this way the speed of revolution is increased to, for example, approximately 1,500 revolutions per minute. A disadvantage is that an expensive gear transmission or other transmission is required. Moreover, this transmission lowers the operational reliability, can require maintenance and increases the mass of that part of the wind turbine that is at the top of the mast. Transmission to ground level is optionally possible, but this gives rise to many complications.

Another possibility is to provide a special generator with which it is possible to generate electrical energy by means of the slowly rotating drive shaft. Such generators have been designed in particular in order to convert the power made available at a low speed of revolution and high torque into electrical power of suitable frequency. However, a generator of this type is heavier and has a substantial higher volume than the gear transmission described above with all the associated disadvantages.

The aim of the present invention is to provide a wind turbine/generator assembly with which the weight of the generator is as low as possible, few moving mechanical parts are present and the generator can be produced relatively inexpensively, without transmission losses and the like occurring.

This aim is achieved with an assembly as described above, in that said generator is a hypocycloid generator, comprising a stator joined to the housing of the assembly and a rotor connected to said shaft, which rotor is designed to execute a rolling movement over a (imaginary) cylindrical surface. The axis of the rotor executes high speed rotation around the axis of this cilindrical surface. The axis of the cilinder coincides with the axis of the circle defined by the axis of the rotor. The turbine can comprise both a wind, water or any other turbine.

It is pointed out that in general hypocycloidal motors are known. However, the use of such a motor as a generator, and more particularly as a generator to be used in combination with a wind turbine, is not suggested in the prior art. By means of the hypocycloidal generator an electrical generator is obtained which has an integral transmission, as a result of which the mechanical power can be made available at a low speed of revolution and the electromechanical conversion takes place at a high internal frequency, as a result of which the machine can remain relatively small, lightweight and inexpensive.

In principle it is possible that the rotor rolls around the outside of the cylindrical surface or, according to a preferred embodiment of the invention, is arranged inside a cylinder. With this arrangement the circle that the centre of the rotor describes preferably has a radius of 5-20/1000 of the internal (free) diameter of the rotor. Here rolling around is understood to include both the situation where the rotor is in direct contact with the stator and the situation where there is a small gap between these components. In the latter case the rotor is supported in some other way, for example by means of rings. The connection between the turbine and the generator can be made in any way known in the prior art. It is possible to fit a universal joint or the like. It must be understood that the difference in axis, that is to say the radius of the circle that the centre of the rotor describes, is relatively small, as can be seen from the above range.

In some cases, more particular at an elongate rotor not being very ridged, it can be desirable to take further steps to keep the rotor in the correct position in the stator. To that end, synchronising means can be provided which can for example be arranged at the front and rear side of such a rotor. Because of that it is always guaranteed that the rotor is accurately positioned and will not take a"sloping"position. It has to be understood that this measure can be used in combination with any hypocycloid generator and even with hypocycloid engine i. e. the use of synchronisation means, of which in example is given below, is not restricted to (wind) turbine generator assemblies.

According to an advantageous embodiment of the invention such synchronisation means comprised spaced set of toothed rings. Both near the cilindrical surface and on the rotor rings are provided which co-operate. A large number of circumferential positions is provided and the rotor will have at least one tooth less to obtain the desired movement.

Because the force of rolling during movement along the path between two teeth is not constant, it can be guaranteed that the rotor is both at the front and the rear side in exactly

the same position. If used as engine, the stator field can be controlled such that a rotary field results dragging the armature with high frequency and have it rolling around in the synchronisationmeans. Because of that the armature executes a rotating movement being much lower than the number of revolutions of other (multi pole) engines with this control frequency. The consequences are lower inertia forces and an engine which can brought to the required speed of rotation very fast. This is in particular of importance when a high reduction at a relatively low power for acceleration of the transmission is necessary. If a set of gears is used often a considerable part of the power is used for acceleration its own mass.

A balance weight can be present to compensate for vibrations, which arise as the rotor rolls around over the stator. In the embodiment in which the rotor rolls around over a path in the interior of a cilinder, preference is given to arranging this balance weight on the outside of such a cylinder. Although in principle it is possible to allow such a balance weight to move with the aid of electromagnetic forces without mechanical coupling, a mechanical link can be present.

Balancing can also be effected in an independent way. With for example a separate electric drive a balancing counter mass can rotate. Rotation of the electric drive can be coupled to rotation of the rotor. For such rotation not much energy is necessary so that a relatively small engine is sufficient.

A completely different possibility is to absorb the effect of vibrations as much as possible. This can for example be effected by a special suspension of several components with (rubber) springs.

According to an advantageous embodiment of the invention, the hypocycloid generator described above is constructed as a so-called short flux generator. With this arrangement the energising chosen is such that the flux"flows"into and out of the rotor via short paths. As a result the force due to magnetism arises when it is required and the nominal transferable torque (for constant other design parameters) can be increased compared with the long flux generator. This energising takes place in such a way that at least two adjacent coils are energised, the polarisation of the magnetic fields being such that the magnetic flux from the one energised pole crosses the air gap to the rotor, crosses via the rotor to the adjacent energised pole of the stator via the air gap and then crosses via the stator back to the first mentioned pole. Energising of the two poles on the stator is such that the magnetic fields of the two poles reinforce one another. With this method of

energising, the polarity of the magnetic field of each pole is opposite to that of the adjacent pole.

By using a large number of poles and energising more than two poles at the same time, the rotor is able to execute a smoother movement.

It has been found that when a balance weight (rotor) is used the generator described above runs without vibration. Incidentally, it is possible to provide such a balance weight with a greater eccentricity than the rotor, as a result of which the mass thereof remains restricted.

This means that in principle it is possible to equip existing designs with the wind turbine/generator assembly according to the invention.

Although it has been described above that a short flux generator is preferred, other windings are possible. The winding such as in accordance with a standard rotary current machine is possible, but according to an advantageous embodiment two sets of windings are used instead of one set of windings, the number of pole pairs being different in the two sets of windings. By this means a homopolar field component is obtained which makes operation as a hypocycloidal machine possible, that is to say permits the rolling around movement of the rotor in the stator.

The homopolar effect can be obtained with the aid of electricity supplied from the outside and/or by the presence of permanent magnets.

Although the invention has been described above with reference to a wind turbine/generator assembly, it will be understood that the generator according to the invention can be employed anywhere, energy being made available in the form of a slowly rotating shaft and a high torque.

The invention will be explained in more detail below with reference to an illustrative embodiment shown in the drawing. In the drawing: Fig. 1 shows, diagrammatically, a side and partially exposed view of a wind turbine/generator assembly according to the invention; Fig. 2 shows different paths and passages through the various components of the device; Fig. 3 shows the section III-III according to Fig. 1, and Fig. 4 is a cross section through a further embodiment of the invention according to line IV-IV in fig. 1.

In Fig. 1 the hypocycloid generator according to the invention is shown in its entirety

by 1. A wind turbine, consisting of a hub 3 on which a number of (in this case two) blades 4 have been mounted, is indicated by 2. The output shaft 6 is mounted in bearing 5. At least the part to the left of bearing 5 is constructed as a universal joint and connected to rotor 7 of the generator 1. Rotor 7 moves inside stator 13, which is rigidly joined to the housing 23 fitted on mast 24. The axis of the rotor is indicated by 10, whilst the axis of the stator is indicated by 18. According to the invention rotor 7 executes a rolling around movement along tracks 16 and 17 which are arranged on either side of the stator. The rotor is provided with tracking rings 11. The various features are designed such that the movement shown diagrammatically in Fig. 2 is executed. If the internal diameter of the stator is approximately one metre, the distance b is approximately 0.5 mm and the distance a approximately 8.5 mm. It is immediately apparent from this that the various relationships in the drawing do not correspond to reality. Such a generator having a diameter of one metre can generate a power of, for example, 1.5 MW. The frequency with which the circle shown in broken lines in Fig. 2 is travelled is many times higher than the frequency of rotation of the rotor. This circle, which is defined by the axes 10, is indicated by 12. In this way an effective transmission is provided, a low speed of revolution with high torque being converted into variation of the gap with high frequency, from which it is possible to generate energy in a simpler manner.

The arrangement of the various coils is shown in Fig. 3.8 indicates the poles of the stator, onto each of which a coil 9 is fitted.

With the construction shown in Fig. 3 there is a so-called shortened flux circuit. With this arrangement flux passes in particular between adjacent pairs of coils of the stator.

A balancing cylinder 20, that rolls around over the track 19 that is arranged on the outside around the stator, is shown highly diagrammatically in Figs 1 and 3. By means of a suitable mechanical drive for cylinder 20 it is possible to allow this cylinder to roll precisely in the opposite phase to the rotor, as a result of which automatic balancing is provided. Electric drive by means of a motor is also possible. By varying the eccentricity of the cylinder, that is to say the maximum gap width between cylinder 20 and track 17, and the mass thereof, the balancing effect can be defined. This eccentricity does not have to be the same as the eccentricity of the rotor with respect to the stator and is preferably greater.

In fig. 4 an embodiment is shown which has slightly been amended relative to the embodiment of fig. 1. At the end of the rotor 7 is a track 17 of stator 13 being provided

with a toothed ring 25. Toothed rings 25 and 26 are provided both on the front and rear side of the rotor. Toothed ring 25 has one tooth less than toothed ring 25 so that the desired movement is obtained. Through this measure optimum synchronisation of the front and rear side of the rotor can be secured under all circumstances.

Of course, lubrication can optionally be provided to allow the rolling movement between the various components to proceed with as little wear as possible. This and further adjustments and modifications are immediately apparent to those skilled in the art on reading the above description and fall within the scope of the appended claims.