GB2312101A

GB2312101A - Multiple rotor motor

Info

Publication number: GB2312101A
Application number: GB9607709A
Authority: GB
Inventors: David Terence Bowman
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-04-13
Filing date: 1996-04-13
Publication date: 1997-10-15
Anticipated expiration: 2016-04-13
Also published as: GB9607709D0; GB2312101B

Abstract

The motor comprises a plurality of members rotatable about a series of substantially parallel or co-axial axes; the members each comprising a series of electromagnets 10,12 carried by a rotatable shaft 1. The electromagnets 10,12 are located substantially symmetrically about the longitudinal axis of the member with the electromagnets 10,12 on adjacent members being axially and circumferentially 50 positioned that, during rotation of the members with respect to one another, an electromagnet 10 on one member is energised when it is brought into closest register with an electromagnet 12 on the adjacent member, but is not otherwise energised. An alternative form having a rotating frame 42 and fixed ring gear 45 is also envisaged.

Description

Title: MOTOR The present invention relates to a novel motor, notably an electrically powered motor.

BACKGROUND TO THE INVENTION: Present forms of electric motor generally comprise a stationary component (the stator) having a series of field coils; and a rotatable component (the rotor) having a series of electromagnets. The rotor is usually mounted on a rotatable shaft within the stator, but this need not be the case, as with the linear motor. Movement of the rotor is caused by passing a current through the coils carried by the rotor and stator. This causes magnetic fields to be set up which interact between the rotor and stator. Constant switching of the current between the coils is required to maintain the electromagnetic forces between the desired portions of the rotor and stator to achieve continuous movement or rotation. In a conventional rotating motor, this switching is achieved through the action of a commutator or a similar device as a result of the relative rotation of the stator and rotor; or can be achieved by microprocessor controlled switching of the current supply to the individual coils.

I have devised a novel form of electric motor which offers advantages over conventional forms of motor.

SUMMARY OF THE INVENTION: Accordingly, the present invention provides a motor which comprises a plurality of members rotatable about a series of substantially parallel or co-axial axes; the members each comprising a series of electromagnets carried by a rotatable shaft, preferably the electromagnets are located substantially symmetrically about, and preferably axially along, the longitudinal axis of the member; the electromagnets on adjacent members being axially and circumferentially so positioned that, during rotation of the members with respect to one another, an electromagnet on one member is energised when it is brought into closest register with an electromagnet on the adjacent member, but is not otherwise energised. The desired sequence of energising can be achieved by suitable switching means or a commutator type of assembly carried by the shafts of the members.

In a particularly preferred form of the motor of the invention, the rotation of adjacent members is synchronised, notably by interlinking the members, eg, by means of co-engaging gear or other drive means carried by the shafts on which the members are mounted.

It is also preferred that the members take the form of a rotatable axle carrying radial protruding cores extending axially along the shaft and upon which are wound the coils for the electromagnets.

In the motor of the invention, power can be taken off from one or more of the members, thus giving flexibility in the design and use of the motor. Also, it is possible to use two or more rotatable members and to increase the power of the motor merely by increasing the number of members used instead of having to increase the size of the members. This enables a designer to configure the motor in a number of forms, whilst retaining the required power output.

The rotatable members are mounted within a suitable framework and this provides the stationary support against which the torque of the motor reacts. The framework can take any desired shape and can be made of a modular construction so that further rotatable members can readily be added to achieve a desired power output.

The motor of the invention can be configured to suit the space within which it is to be mounted, giving the designer of machinery incorporating it greater design flexibility. As described below, a number of the rotatable members can surround a single power take off shaft so that the motor can be of circular shape. In such a motor, the rotatable members can be fixedly mounted with a circumferential frame or can be held within the frame by a gear ring which allows the members to rotate and precess within the gear ring.

It is also within the scope of the present invention to mount the members transversely within a support frame to which is connected a longitudinal power output shaft. The members carry a gear wheel at one end, which engages with a static gear ring generally co-planar with the frame and the axes of the members. Rotation of the members within the frame causes the gear wheels carried by the members to travel around the gear ring to rotate the frame and the output shaft.

DESCRIPTION OF THE DRAWINGS: To aid understanding of the invention, it will be described with respect to the preferred form as shown in the accompanying drawings, in which: Figure 1 is a diagrammatic side view of two of the rotatable members carrying the electromagnets; Figure 2 is a plan view from above of one pair of the members of Figure 1; Figure 3 shows the sequence of events for a commutator serving an electromagnet in the motor of Figure 1; and Figure 4 is a vertical section through an alternative form of the motor of the invention.

DESCRIPTION OF A PREFERRED EMBODIMENT: With the form of motor shown in Figures 1 and 2, the shaft 1 for each rotatable member is mounted in a suitable bearing so that the shaft can rotate. Typically, the shaft 1 will be journalled in a sleeve, ball or roller bearing housed in a suitable support framework.

The shaft 1 of each rotatable member rotates about an axis which is substantially parallel to the axis of rotation of the other rotatable members in the motor. However, in an alternative form of the motor, each member consists of a disc carrying the electromagnets on one face thereof and extending radially from a central transverse shaft. Two discs are mounted with the electromagnet carrying faces opposed to one another so that the discs rotate about a substantially common axis. Alternatively, one disc can be fixed with the other being rotatable. For convenience, the invention will be described below in terms of the parallel shaft motor.

Whilst each shaft is free to rotate about its axis, the rotation of each rotatable member in the motor is preferably interlinked to the rotation of the other members in the motor. This interlinking is conveniently achieved by means of intermeshing gear wheels 4 at either or both ends of each shaft 1. Other forms of interlinking may be used, for example toothed belt drives or chain linkages, or by forming the co-operating surfaces of adjacent members with axial flutes or castellations which engage one another like gear wheels.

The function of the interlinking is to ensure that, as one rotatable member rotates, the adjacent member rotates in synchrony so as to bring the electromagnets on the adjacent members into register with one another and thus cause a new set of magnetic forces to come into play to continue the rotation of the rotatable members.

The shafts 1 of the rotatable members are journalled in a suitable support framework housing the motor and the power is taken off from the rotatable members via one of the axial shafts 1 or from another member driven from such a shaft. Thus, the rotatable members can be mounted within an outer ring member driven by all the rotatable members of the motor acting on it directly or through a series of intermediate gears. It is also possible to have the gear ratios for some of the gears 4 interlinking the shafts 1 with other than 1:1 ratios, so that one or more of the shafts is rotating at a different speed to the others. In this case, it will usually be desired that the differently geared shaft be a lay shaft.

The above simple construction of the motor of the invention can be modified, for example by the addition of further rotatable members to increase the power output of the motor. Such other rotatable members can be grouped to form a unit with the shaft axes on a grid pattern containing an even number of units all interlinked to at least two other units. An odd number of units may be used if desired, but one of the units can be interlinked with only one other unit in that case. The units can be built up in a number of configurations, eg. on a grid plan with power take off at one or more points; as a radial configuration with the rotatable members grouped in a ring around a central member or power take off shaft. This latter configuration is of especial use where the motor is incorporated into a drive hub or where the central member takes the form of a fixed shaft and the rotatable members precess around that shaft to drive an outer gear wheel, eg. for driving track laying vehicles.

In the form of the motor shown in Figure 4, the shafts 41 are located transversely in a framework 42 which carries a fixed power take off shaft (not shown) extending out of the plane of the drawing and mounted in suitable bearing so the take off shaft and the framework 42 can rotate.

Each shaft 41 carries the axial electromagnets 43 similar to those described below. One end of each shaft 41 carries a gear wheel 44 which engages with a gear ring 45 whose plane is substantially parallel to the axes of the shafts. The gear ring 45 is secured to the housing 46 of the tool or other article in which the motor is mounted.

Such a motor provides an axially compact motor which may be of benefit in hand held power tools.

In the motor of the invention, the electromagnets carried upon the shafts 1 are typically in the form of a coil 10 wound around a ferromagnetic core 11. The core can take the form of a generally cylindrical rod of a ferromagnetic material mounted substantially radially on the shaft 1.

However, a particularly preferred construction is to mount generally rectangular cores substantially axially on the shaft. Preferably, the cores are arranged as axial lines of separate segments, each with its own energising coil.

Typically, the cores are mounted at 150 intervals tangentially around the circumference of the shaft. Where the shaft and its associated electromagnets are housed within an outer housing, the axial cores and their coils can be housed in the flutes of a stellate cross-section housing so that the flutes of adjacent housings intermesh.

They may be used to provide the interlinking of the rotation of the members in place of and/or in addition to gear wheels carried adjacent the ends of the shafts of the members.

The polarity and power of the electromagnets can be varied rapidly and simply by suitable switching of the current passed through the coil. This enables the repulsion/attraction sequence when magnets are brought into register to be finely tuned to ensure optimum performance. Thus, the shaft 1 can carry a commutator 12 having a number of sections for each electromagnet or set of magnets at each axial level on the shaft. The commutator 12 can have sufficient sections 14 to achieve the desired switching on and off of the coils as they approach and pass through the registration position.

The commutator 12 can be of conventional design and construction and is conveniently mounted on the shaft 1 to engage the appropriate number of static brushes 13 having current fed thereto via a suitable switching gear.

However, it is particularly preferred that the commutator be in the form of a series of sectors on a transverse plate mounted adjacent the end of each rotatable member with the brushes acting axially onto the face of the plate. The plate face is divided into the requisite number of sectors by suitable insulating means to form the segments of the commutator.

The motors of the invention offer the ability to construct a motor from standard rotatable members which are then coupled together to give a motor of the desired power output and of the desired physical dimensions to suit the location it is to be fitted into. The power can be taken off at any suitable point from the motor and not only from a central shaft. The motor of the invention does not require the bulky housing that normal motors require, since many of the forces generated within the rotating members and the motor are counterbalanced by reactions within the motor itself; notably each rotatable member acts on and is reacted on by the adjacent rotatable members due to the electromechanical/physical interlinking of their rotation. It is also possible to construct the motor as a modular unit having the facility to add-on further units to increase the power of the basic unit either temporarily or for prolonged use where the load on the motor exceeds that for which the motor was originally designed.

The motor of the invention has been described above in terms of rotatable members built up around a shaft or cylinder. However, the characterising feature of the design of the motor of the invention is the use of a series of electromagnets mounted on a rotatable body cooperating with similar units. The units can be built up from electromagnets mounted on a support and this support then mounted in a resin or other rigid support to form each rotatable member. The motor of the invention can thus be made from standard, cheap and lightweight units which are assembled together in the desired number and configuration for the desired end use.

The motor of the invention can incorporate other features to enhance its performance. Thus, the control of the feed of current to the coils can be by means of a microcomputer; or sleeper magnets can be mounted around the periphery of the motor to act on the exposed faces of the outermost rotatable members and thus give an initial thrust to start the motor from rest. It may also be desired to locate a ferromagnetic or similar material between the rotatable members to act as a magnetic flux guide in the region of the nip gap between the members.

This guide can extend through the nip gap to act as a magnetic bridge between the opposed magnetic sectors of the rotatable members.

In a particularly preferred form, the present invention provides an electrically powered motor which comprises a plurality of members rotatable about a series of substantially parallel axes; the members each comprising a series of electromagnets located axially along the longitudinal axis of the member and each arranged transversely to the axis of the member; the magnets on adjacent members being axially and circumferentially so positioned that magnets on adjacent members are brought into register with one another whereby attractive and/or repulsive forces between registering magnets are generated and cause rotation of the members; the members being provided with gearing or other means for interlinking the rotation of the members to one another; motive force being taken off from the motor via one or more of the rotatable members or via a member driven by one of the members.

Preferably, the electromagnets on one member are tangentially displaced from those on adjacent members by an angle of a multiple of 150 and the members are interlinked whereby they rotate in synchrony with one another. It is also preferred that the electromagnets are energised by means of a commutator assembly such that the magnets are energised as they approach the position of closest register with the magnets on adjacent rotatable members to provide an attractive force between the magnets, are de-energised at the position of closest register and are energised in the opposite sense as they leave the position of closest register to provide a repulsive force between the magnets.

The motors of the invention find widespread use where an electric motor is required. We believe that the amount of copper required in the manufacture of the motors of the invention may be less than that required for a motor of conventional design and construction having a similar power output. This saving in weight per unit of power output is of particular advantage with large motors, typically those in excess of 10 HP. The ability to select the configuration of the motor to suit the physical space into which it can be fitted is an attribute not available with conventional motors. Also, the motor of the invention enables power to be taken off from the opposed ends of the shafts of two rotatable members so that the load on one shaft provides the reaction against which the load on the other shaft acts. The motor of the invention can thus be used in driving vehicles, such as wheel or invalid chairs or warehouse trolleys, without the need to provide a differential gear in the drive axis.

Claims

1. A motor which comprises a plurality of members rotatable about a series of substantially parallel or coaxial axes; the members each comprising a series of electromagnets carried by a rotatable shaft, preferably the electromagnets are located substantially symmetrically about, and preferably axially along, the longitudinal axis of the member; the electromagnets on adjacent members being axially and circumferentially so positioned that, during rotation of the members with respect to one another, an electromagnet on one member is energised when it is brought into closest register with an electromagnet on the adjacent member, but is not otherwise energised.

2. A motor as claimed in claim 1, in which the desired sequence of energising is achieved by a commutator type of assembly carried by the shafts of the members.

3. A motor as claimed in claim 1 or claim 2, in which the rotation of adjacent members is synchronised by interlinking the members.

4. A motor as claimed in any preceding claim, in which the members take the form of a rotatable axle carrying radial protruding cores extending axially along the shaft and upon which are wound coils for the electromagnets.

5. A motor as claimed in any preceding claim, in which the rotatable members are mounted within a framework.

6. A motor as claimed in any preceding claim, in which a number of the rotatable members surround a single power take off shaft so that the motor can be of substantially circular shape.

7. A motor as claimed in claim 6, in which the rotatable members are fixedly mounted with a circumferential frame.

8. A motor as claimed in claim 6, in which the rotatable members are held within the framework by a gear ring which allows the members to rotate and precess within the gear ring.

9. A motor as claimed in any preceding claim, in which the members are mounted transversely within a support frame to which is connected a longitudinal power output shaft.

10. A motor as claimed in claim 9, in which the members carry a gear wheel at one end, which engages with a static gear ring generally co-planar .with the support frame and the axes of the members.

11. A motor substantially as herein described, with reference to and as shown in the accompanying drawings.