GB2339082A

GB2339082A - Motor/gear drive arrangement of the cycloid type

Info

Publication number: GB2339082A
Application number: GB9821845A
Authority: GB
Inventors: Michael John Flowerday
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-07-02
Filing date: 1998-10-08
Publication date: 2000-01-12
Also published as: GB9821845D0; GB9814260D0

Description

2339082 PATENT APPLICATION In the name of Michael John Flowerday of 24

Kennedy Avenue, Gorleston, Great Yarmouth, Norfolk, England, a British Subject.

IMPROVEMENTS TO MOTORS NTH INTEGRAL CYCLOIDAL GEAR BOXES Many forms of motor, electric or otherwise, axial or radial, may be fitted with a gear box or may be manufactured to include a gear box. One common feature is that the motor shaft, turned by the rotor, rotates at a higher or lower speed than the gearbox output shaft. Many types of gearbox may be employed.

One particular gearbox arrangement, the eccentric or cycloidal type, incorporates or accepts an input shaft which causes indirectly, via a bearing or bearings eccentrically mounted on such an input member, an external gear or gears variously formed to rotate eccentrically within a fixed internal gear or gears. The resultant relative circular rotation of the external gear or gears, caused by the difference in the number of teeth between the external and internal gears is transmitted to the output shaft by any one of a variety of mechanisms. Such devices have been patented and are well known in various forms. In each form by design or during manufacture efforts are made to balance the eccentrically rotating parts, and such methods form the content of various patent applications.

According to the present invention an axial or radial motor with an integral gearbox comprises a motor wherein the rotor of the motor, mounted around or within suitable bearings, is made to rotate freely around a central shaft without direct connection to it.

In one arrangement an additional bearing is mounted on to an eccentrically turned section of the freely rotating rotor and around this is mounted an external gear to provide the input stage of a cycloidal gearbox. The rotor, eccentrically mounted bearing and gear may then be balanced as one item. The large mass of the rotor enabling such balancing to be effected easily, using known techniques, without the need for the use of a counterbalancing second eccentric gear or any special parts.

In a second arrangement an additional bearing is mounted on to an eccentrically turned extension of a freely rotating rotor. This bearing supports two external gears. These gears are directly coupled together. Each gear is made to rotate around and within a separate external gear. The first external gear is fixed. The second external gear is directly connected to the common output shaft which may run through the complete motor gearbox, providing an output shaft with good mechanical rigidity and drive from both ends if required. Such a twin geared arrangement may provide within a very short length a very high reduction ratio, the gear arrangement producing a differential output. Again the twin bearing mounted gears and the rotor assembly may be balanced as one item, the rotor providing sufficient shape and mass for this to be achieved.

2.

Another arrangement employs a bearing, eccentrically mounted or created within the rotor within which is mounted an internal gear. This gear is made to oscillate without rotation around an external gear which is directly connected to the common output shaft around which the rotor circularly, freely, is caused to rotate.

One arrangement of this later case is shown with a freewheel interposed between the driven external gear and the output shaft, providing an output shaft that may be rotated freely or driven by the rotation of the rotor.

The objects of the invention are to provide:

an axial geared motor of very short length comprised of a motor incorporating a stator, a rotor and a cycloidal gear arrangement, which may be easily balanced, provided by at least one eccentrically rotating rotor mounted bearing with an external gear, rotating around and within a fixed internal gear, providing via an output mechanism a reduced rotor speed and increased torque to a common output shaft which is available at each end if required. The maximum rotor speed reduction may be in the order of 150:1.

a radial geared motor of short length comprised of a motor incorporating a stator and a rotor and a cycloidal gear arrangement, which may be easily balanced provided by at least one eccentrically rotating rotor mounted bearing with an external gear, rotating around and within a fixed internal gear, providing via an output mechanism a reduced rotor speed and increased torque to a common output shaft which is available at each end if required. The maximum rotor speed reduction may be in the order of 150:1.

an axial geared motor of very short length comprised of a motor incorporating a stator and a rotor and a cycloidal gear arrangement, which may be easily balanced, provided by at least one eccentrically rotating rotor mounted bearing with an external gear rotating within a fixed internal gear and another external gear directly fixed to the outer eccentrically rotating gear and mounted on the same eccentric rotor extension. This additional eccentrically rotating gear being made to rotate around and within a second internal gear which is directly connected to a common output shaft which is available at each end if required. Selection of a common offset distance and difference in the numbers of teeth between the first and second stages provide a reduced rotor speed and an increased torque to the common output shaft. The rotor speed reduction may be in excess of 1000.- 1.

an axial geared motor of very short length comprised of a motor incorporating a stator and a rotor complete with a cycloidal gear arrangement provided by at least one eccentrically oscillating rotor mounted internal gear oscillating around an external gear 3.

connected directly to the common output shaft. This provides a reduced rotor speed and increased torque to the common output shaft which is available at each end if required. The maximum rotor speed reduction may be in the order of 150:1.

Examples of the present invention will now be described with reference to the accompanying drawings listed below.

Fig. 1 A sectioned view of an axial geared motor incorporating a rotor mounted cycloidal gear arrangement using an eccentrically rotating rotor mounted bearing and external gear and a fixed internal gear complete with a common output shaft. Fig. 2 A sectioned view of a radial geared motor incorporating a rotor mounted cycloidal gear arrangement using an eccentrically rotating rotor mounted bearing and external gear and a fixed internal gear complete with a common output shaft. Fig. 3 A sectioned view of a axial geared motor incorporating a rotor mounted two stage cycloidal gear arrangement using an eccentrically rotating rotor mounted bearing and two external gears. The first rotating within and around a fixed internal gear, the second rotating within and around an internal gear directly coupled to or part of the common output shaft. Fig. 4 A sectioned view of an axial geared motor incorporating a rotor mounted cycloidal gear arrangement using an eccentrically oscillating rotor mounted internal gear oscillating around an external gear directly mounted on a common output shaft. Fig. 5 A sectioned view of an axial geared motor incorporating a rotor mounted cycloidal gear arrangement using an eccentrically oscillating rotor mounted internal gear oscillating around an external gear driving concentrically a freewheel directly mounted on a common output shaft.

Fig 1. Shows an electric axial geared motor, representatively drawn to incorporate, for the sake of clarity a switched reluctance rotor. Other stator rotor relationships may be envisaged, for example induction and permanent magnet motor types also other types of motor such as air or hydraulic. In this case the operation of such a switched reluctance motor is well known therefore it will not be discussed here.

The rotor 2 is supported by a rotor bearing 12 and may be made to freely rotate around the output shaft 22. The rotor 2 supports eccentrically a bearing 4 around which is mounted an external gear 5. This gear has a number of holes 19 provided around a 4.

suitable pitched circle diameter of such a size as to allow engagement with a circular array of pins 7 mounted within and around the output disk 8, which is mounted on or maybe part of the common output shaft 22.

The rotation of the rotor 2 and the subsequent indirect eccentric rotation of the external gear 5 within and around the fixed internal gear 6 which is concentric with the output shaft 22 causes the external gear to impart a circular torque to the pins 7 thereby turning the output disc 8 and shaft 22. This operation of a cycloidal gear arrangement is well known and will not be elaborated.

During the manufacture ihe rotor 2 with bearings 12, 4, and external gear 5 are balanced as a unit to rotate circularly around the shaft 22 at the required rotor speed. Since the rotor 2 is of large mass and may be easily drilled etc., such balancing is easily achieved without modification or addition to the eccentric portion supporting the bearing 4. as for example is shown in Patent No WO 88/05508.

The elimination of a motor output shaft between the rotor 2 and the first stage of the gear arrangement which would be supported by a gear box input or motor output bearing, not shown, allows such a simple balancing operation to be achieved. There is no mechanical isolation at the rotor from vibration caused by the eccentric operation of the gear arrangement, by an inter-stage or motor output bearing. Therefore the vibration caused may be eliminated by simply balancing the assembly.

Another example is shown in Fig.2, again drawn to represent a switched reluctance motor. The radial geared motor shown in Fig.2 operates in the same way as the axial motor in Fig. 1 with the exception that the output drive from the eccentrically rotating external gear 5 around and within the fixed internal gear 6 is taken via a hollow Oldham Coupling formed with the face of gear 5 and the output disc 8 which is directly connected to or may be part of the output shaft 22. The operation of such a coupling with its coupling dis 9 and the gear arrangement is well known.

Here again the manufacture of the complete assembly of the rotor 2 with bearing 12, 4 and external gear 5 may be easily balanced to rotate circularly around the shaft 22 at the required rotor speed.

Another example of the present invention may be seen in the axial geared motor shown in Fig. 3. The axial motor shown is different from that shown in Fig. 1 in the way that the rotor 2 is extended and supported by bearings 12 and 13. Here again any suitable stator rotor arrangement or motor type may be employed.

In Fig. 3 the output shaft is supported between bearings 20 and 21. The rotor 2 is supported by bearings 12, a combined needle thrust bearing and 13, a standard needle bearing. The rotor 2 may be made to rotate freely around shaft 22.

5.

The rotor 2 supports eccentrically one long needle bearing 4 around which is mounted two external gears 5 and 10. These two external gears 5 and 10 are coupled directly together, they may have different numbers of teeth. As before in examples Fig. 1 and Fig.2 the rotor 2 rotates circularly around the output shaft 22 causing the external gears 5 and 10 to rotate eccentrically, gear 5 within and around the fixed internal gear 6 and gear 10 within and around the internal gear 11, which is directly coupled or fixed to the output shaft 22 via the output disc 8.

These two inter-related gear sets 5 with 6 and 10 with 11 provide a differential gear arrangement which is well known. It is usual where a separate flange mounted cycloidal gearbox such as shown in Figs. 1,2 or 3 is used, for a second first stage gear to be used. That is to say gears 5 and 6 are duplicated being eccentrically mounted around a bearing but 1800 displaced from 5 and 6. This is done to eliminate the first stage out of balance. In the example shown in Fig. 3, whether or not a second first stage gear set is employed it is still necessary to balance for the eccentric motion of the external gear 10.

Here in Fig. 3 the ability to use this rotor born arrangement, where the rotor 2 directly supports at least two external gears 5 and 10 via bearing 4, allows the whole assembly of rotor 2, bearings 12 and 4, and gears 5 and 10 to be balanced as one item at the required circular speed. The larger diameter afforded by the rotor 2 of an axial motor compared with a radial motor of the same power also assists in making the simple task of balancing the assembly much easier.

The axial geared motor shown in Fig. 4 again, for clarity only, is shown as a switched reluctance motor. In this motor the rotor 2 is eccentrically bored or otherwise made to receive a large diameter bearing 14 within which the internal gear 16 would be free to rotate were it not for the circular array of fixed pins 7 protruding into suitably sized holes drilled in the gear 16. The resultant action is for the gear 16 to oscillate around the shaft mounted gear 15 causing the shaft 22 to rotate. The shaft being supported by bearings 20, drive being shown to be available from both ends.

In some cases the bearing 14 may be omitted. The interface between the outside of the gear 16 and the inside of the rotor 2 creating a suitable bearing interface, the two surfaces being suitably prepared.

The rotor 2 complete with bearings 12 and 14 and internal gear 16 may be simply balanced as a unit to rotate at rotor speed around the shaft 22.

Fig. 5 shows a special case of the axial motor gearbox described above Fig.4. The motor arrangement in this case is a single sided permanent magnet rotor axial pole motor. The operation of the rotor 2 and gear set 15 and 16 together with bearings 12 and 14, pins 7 and holes 19 is almost identical to that described for Fig. 4. The one exception is that a freewheel 18 has been concentrically inserted between the external gear 15 and the output shaft 22 to provide an output shaft that may either be externally 6.

freely rotated or driven by the axial motor gear arrangement. This was designed for use in a cycle.

Within the above descriptions the bearings used, the gear profiles and type of alternative designs used to produce them, for example pins and holes, the types of rotary power provided to turn the rotor, double ended or single ended shafts, these and other details may all be selected as required together with suitable materials for manufacture.

It will be clear to those with knowledge of cycloidal gear arrangements that other arrangements similar to those shown in Figs 1 and 2 may be provided, (not shown), wherein the common shaft 22 is fixed relative to the stator 1, the internal ring gear 6, suitably mounted, being free to rotate, the output drive being taken directly or indirectly from the ring gear.

7.

Claims

Claims.

1. An axial or radial geared motor comprised of a stator rotor construction wherein the stator is fixed and the rotor is made to rotate freely, circularly, around a common output shaft which may extend through the motor, such rotor supporting eccentrically and indirectly via a bearing or bearings at least one external gear, which in combination with a fixed internal gear provides a single stage cycloidal gear arrangement providing torque to rotate a common output shaft, the rotor and bearing mounted gear assembly being balanced as one item at the desired rotor speed.

2. An axial or radial geared motor comprised of a stator rotor construction wherein the stator is fixed and the rotor is made to rotate freely, circularly, around a common output shaft which may extend through the motor, such rotor supporting eccentrically and indirectly via a bearing or bearings at least two directly coupled external gears, which in combination with one fixed internal gear and one internal gear directly coupled to the output shaft provides a differential cycloidal gear arrangement providing torque to rotate a common output shaft, the rotor and bearing mounted gear assembly being balanced as one item at the desired rotor speed.

3. An axial or radial geared motor comprised of a stator rotor construction wherein the stator is fixed and the rotor is made to rotate freely, circularly, around a common output shaft which may extend through the motor, such rotor supporting eccentrically and indirectly via a beaMg or bearings at least one internal gear, which in combination with one external gear directly coupled to the output shaft provides a single stage cycloidal gear arrangement providing torque to rotate the common output shaft, the rotor and bearing mounted gear assembly being balanced as one item at the desired rotor speed.

4. An axial or radial geared motor comprised of a stator rotor construction wherein the stator is fixed and the rotor is made to rotate freely, circularly, around a common output shaft which may extend through the motor, such rotor supporting eccentrically and indirectly via a bearing or bearings at least one internal gear, which in combination with one external gear directly coupled to the output shaft provides a single stage cycloidal gear arrangement providing torque to rotate the common output shaft through a freewheel device interposed between the external gear and the output shaft, the rotor and bearing mounted gear assembly being balanced as one item at the desired rotor speed.

5. An axial or radial geared motor as in Claim 1 wherein the common shaft is fixed relative to the stator, the internal gear, suitably mounted, being free to rotate thereby providing directly or indirectly the output drive, the rotor and bearing mounted gear assembly being balanced as one item at the desired rotor speed.