Field of the Invention.

The present invention is concerned with an electric machine. More specifically, the present invention is concerned with an electric machine providing motive force for an electric vehicle.

Background of the Invention.

Electric motors are one form of electric rotary actuator and use an electric input to produce a mechanical rotary output (a torque). Such motors are used in a wide variety of technical fields, and different types of motor are used for different applications, depending on the nature of the electrical input (e.g. AC/DC, phase etc) and the nature of the mechanical output required (high force low speed, low force high speed).

Known electric machines exhibit several problems.

Firstly, copper is often used for the rotor and/or stator windings. Copper is both expensive and heavy. Due to demand in recent years and increasing demand for the future as electrical actuation becomes more prevalent, it is likely to further increase in cost.

There is a drive to make electric machines more efficient both to manufacture and to operate (i.e. in terms of the percentage of energy successfully converted to the desired form of output). Improvements such as low friction materials for the rotor bearings, low friction brushes in brushed motors, high efficiency gear trains and such like have provided incremental increases.

Many motors in particular are used in applications where it is highly beneficial to be as light as possible. Motors for actuation in vehicles in particular benefit from being lighter, because the overall efficiency of the vehicle can be reduced. This benefits commercial aircraft, UAVs as well as electric and hybrid automobiles.

Higher efficiency is beneficial for battery powered motors because the batteries will last longer, thereby reducing the frequency of battery changes as well as the cost and environmental impact of battery production and disposal.

Due to the level of precision required in motor design, as well as the high part count, electric machines can often make up the bulk unit cost of many products, particularly domestic products. As such, there is a need to reduce the cost of motors which will have a significant beneficial effect on the cost of the overall product. A further disadvantage of known electric machines is that high power motors require significant current at the motor terminals. This is a safety concern.

A yet still further disadvantage is that electric machines emit radio frequency signals which may interfere with other electronics.

In some electric motors, it is necessary to know the rotational position of a pole of the rotor with respect to some datum such as a stator winding to enable the electric motor controller to energise the correct stator windings in the correct sequence for a fast and efficient operation of the motor. Typically, one or more Hall effect sensors are embedded in the stator to detect poles of the rotor during motor operation. The Hall effect sensors may also be used to obtain an estimated initial starting position of the rotor. A common problem, however, with this arrangement is that the initial starting position is often provided within an estimated but large window of rotation such as, for example, 60 degrees and this can prevent efficient and fast starting of the motor.

For electric vehicles, both hybrid and fully electric, and for other electric motor applications, the normal design methodology is to select an electric motor or a group of electric motors which will provide optimal power output meaning that the motors will be over- sized for the application to enable the motors to operate in the first third of their efficiency curve (Fig. 3a). This leads to a power to weight problem in the vehicle, system or machine in which said electric motor or group of electric motors is installed. Once an electric motor or group of electric motors is selected, a drive controller is typically selected which must have the capacity to provide the electric motor or group of electric motors with sufficient power to operate, i.e. the drive or motor controller must be able to supply the electric motor or group of electric motors with the required voltage and current in the format (AC or DC) needed. In electric vehicles, a battery system must also be selected with the capacity to provide sufficient power for a run duration. This mode of designing systems, etc. utilising electric motors has typically been used for electric vehicles such that it has been necessary to develop very high capacity, sophisticated drive controllers and very high capacity (very high voltage, very high current) cables for interconnecting the battery system, drive controller and the one or more electric motors. The wiring looms comprising such cables can amount to a significant cost element in the manufacture of the electric vehicle. Furthermore, the wiring looms present several dangers due to the high voltage and high currents they carry.

Other problems are exhibited in many existing electrical vehicles due to the foregoing design methodology. For example, high currents from the battery system leads to switching issues in the drive controller electronic circuits/printed circuit boards (PCBs) and this has required a range of expensive switching solutions to be developed. In some electric vehicles, the operating voltage has been set high enough to allow a lower operating current, but high operating currents are still common which lead to inherent safety issues and also leads to a high cost in the control electronics due to switching and current handling issues.

As the electric motor or group of electric motors is sized for the application, efficiency of the motor(s) will be lower, often as low as 40%, in order to gain the highest power output range. If, on the other hand, the electric motor or group of electric motors is/are sized for efficiency, the arrangement will be both more expensive and heavier. The lower efficiency option leads to a general reduction in electric vehicle potential range. However, for the higher motor efficiency option, the heavier motor(s) leads to the same issue in that, whilst the motor(s) nominally runs at a more efficient operating range, the reduction in power to weight ratio is significant. Furthermore, both cables and connectors in the wiring loom have to be sized to carry the high voltage and current required by the system.

Objects of the Invention.

An object of the invention is to mitigate or obviate to some degree one or more problems associated with known electric machines for vehicles.

The above object is met by the combination of features of the main claims; the sub claims disclose further advantageous embodiments of the invention.

Another object of the invention is to provide an improved electric machine.

One skilled in the art will derive from the following description other objects of the invention. Therefore, the foregoing statements of object are not exhaustive and serve merely to illustrate some of the many objects of the present invention.

Summary of the Invention.

The invention generally relates to an electric machine having a primary mechanical output, a plurality of electric sub-machines configured to drive the primary mechanical output, and an array of motor controllers, each motor controller being configured to control a subset of the plurality of electric sub-machines. The electric machine can be used for many functions including as drive units for electric vehicles. An electric vehicle may comprise an electrical energy storage system, at least one electric machine for providing motive force to the vehicle, said at least one electric machine having a plurality of electric sub-machines configured to drive a primary mechanical output thereof, and an array of motor controllers, each motor controller being configured to control a subset of the plurality of electric sub machines, wherein each motor controller is connected to its subset of the plurality of electric sub-machines by cables sized in relation to a maximum power amount required by said subset of the plurality of electric sub-machines during operation.

According to a first aspect of the invention there is provided an electric machine comprising: a primary mechanical output; a plurality of electric sub-machines configured to drive the primary mechanical output; and an array of motor controllers, each motor controller being configured to control a subset of the plurality of electric sub-machines.

Preferably, a subset of the plurality of electric sub-machines comprises one electric sub-machine, i.e. there is a motor controller for each electric sub-machine.

Preferably, each motor controller is connected to its subset of the plurality of electric sub-machines by cables sized in relation to a maximum power amount required by said subset of the plurality of electric sub-machines during operation.

Preferably also, each motor controller is located in close proximity to its subset of the plurality of electric sub-machines and may be located in a housing of the electric machine. The motor controller may be accommodated within an endcap of the electric machine or electric sub-machine.

Preferably, cables connecting an electrical energy storage device to a motor controller are sized in relation to a maximum power amount required by said motor controller’s subset of the plurality of electric sub-machines during operation. Similarly, conductive paths on one or more circuit boards of the motor controller are sized in relation to a maximum power amount required by said motor controller’s subset of the plurality of electric sub-machines during operation.

Any of cables connecting the motor controller to its subset of electric sub-machines, cables connecting an electrical energy storage device to the motor controller, or conductive paths on one or more circuit boards of the motor controller are preferably low voltage cables or conductive paths. Similarly, electrical connectors for any of cables connecting the motor controller to its subset of electric sub-machines and/or cables connecting an electrical energy storage device to the motor controller are sized in relation to a maximum power amount required by said motor controller’s subset of the plurality of electric sub-machines during operation.

According to a second aspect of the invention there is provided an electric vehicle including an electric machine according to the first aspect of the invention. According to a third aspect of the invention there is provided an electric vehicle comprising: an electrical energy storage system; a plurality of electric machines for providing motive force to the vehicle; an array of motor controllers, each motor controller being configured to control a subset of the plurality of electric machines.

According to a third aspect of the invention there is provided an electric vehicle comprising a wiring loom for an electric vehicle having an electrical energy storage system, a plurality of electric machines for providing motive force to the vehicle, and an array of motor controllers, each motor controller being configured to control a subset of the plurality of electric machines, the wiring loom comprising: cables connecting each motor controller to its respective subset of said of the plurality of electric machines wherein said cables are sized in relation to a maximum power amount required by said motor controller’s subset of the plurality of electric machines during operation.

According to a fourth aspect of the invention there is provided an electric vehicle comprising a wiring loom for an electric vehicle having an electrical energy storage system, an electric machine for providing motive force to the vehicle, and an array of motor controllers, each motor controller being configured to control a subset of a plurality of electric sub-machines comprising said electric machine, the wiring loom comprising: cables connecting each motor controller to its respective subset of said of the plurality of electric sub-machines wherein said cables are sized in relation to a maximum power amount required by said motor controller’s subset of the plurality of electric sub-machines during operation.

According to a fifth aspect of the invention there is provided an electric machine comprising: a primary mechanical output; a plurality of electric sub-machines configured to drive the primary mechanical output, each of said plurality of electric sub -machines having a rotor with a known rotational relationship with the primary mechanical output; wherein two or more of said plurality of electric sub-machines includes a rotor position detector device; and wherein at least one of said two or more electric sub-machines has its rotor rotationally offset by a set amount relative to a rotor of at least one other of said two or more electric sub-machines.

Each rotor position detector device may comprise one or more Hall effect sensors which may be embedded into respective stators of said two or more electric sub-machines.

The set amount for rotationally offsetting the rotor of one of said two or more electric sub-machines with respect to a rotor of another of said two or more electric sub-machines may comprise a selected, predetermined, or calculated amount which may be less than 180°/N, where N is a number of stator winding pairs in each of said plurality of electric sub machines.

Preferably, at least half of said plurality of electric sub-machines includes a rotor position detector device wherein each of said electric sub-machines including a rotor position detector device has its rotor rotationally offset relative to rotors of remaining ones of said electric sub-machines including a rotor position detector device.

More preferably, all of said plurality of electric sub-machines includes a rotor position detector device wherein each of said plurality of electric sub-machines has its rotor rotationally offset relative to rotors of remaining ones of said plurality of electric sub- machines.

Preferably also, initial rotor positions on start up for some or all of said plurality of electric sub-machines are derived, extrapolated, or calculated from rotor position signals provided by said rotor position detector devices.

A rotor of one of said plurality of electric sub-machines may be rotationally offset by a set amount relative to at least one other of said plurality of electric sub-machines by indexing a mechanical output of said one of said plurality of electric sub-machines with respect to the primary mechanical output.

Preferably, there is provided a controller configured to: monitor a parameter of the electric machine indicative of the power of the electric machine; and, engage or disengage one or more of the plurality of electric sub-machines dependent upon the monitored parameter, so as to increase the number of sub-machines simultaneously driving the primary mechanical output at higher electric machine powers. There are various methods of engagement and disengagement: Each of the sub -machines may comprise a rotor, in which each rotor is configured to be mechanically disengaged from the mechanical input or output to disengage the respective sub-machine. For example, each rotor may be connected to the input or output shaft by a clutch. Each of the sub-machines may be configured to be selectively electrically disengaged. In other words, the power input/output to the sub-motor may be disconnected, electronically or mechanically.

In a further alternative, each of the sub-machines may comprise a rotor and a stator, in which at least one of the rotor and stator can be moved to reduce their electromagnetic interaction upon disengagement. In other words, the rotor and stator can be moved further apart. In the case of a brushless motor, the stator can be moved to reduce the drag on the stator caused by inducing a current in the stator winding. Preferably the monitored parameter is representative of electrical power consumed. This may be in the form of a current and voltage measurement.

The controller is preferably configured to store sub-machine usage information, engage and disengage each sub-machine based on the sub-machine usage information. The controller may be configured to engage sub-machines with lowest usage first and configured to disengage sub-machines with highest usage first. The controller may be configured to engage a further sub-machine of the plurality of sub-machines at a power interval, in which each sub-machine has a maximum rated power of at least twice the power interval. This ensures that for typical electric motors, they are operated at peak efficiency, rather than maximum power (which is less efficient). More preferably each sub-machine has a maximum rated power of at least three times the power interval.

According to a sixth aspect of the invention there is provided an electric machine comprising: a primary mechanical output; a plurality of electric sub-machines configured to drive the primary mechanical output, each of said plurality of electric sub -machines having a rotor; wherein only one of said plurality of electric sub-machines includes a rotor position detector device; and wherein relative rotational positions of the rotors of all of the plurality of electric sub-machines with respect to the primary mechanical output are known.

Preferably, the rotor position signals from said rotor position detector device are used to control each of said plurality of electric sub-machines.

According to a seventh aspect of the present invention there is provided an electric machine comprising: a primary mechanical output or input, a plurality of electric submachine rotors, a plurality of electric sub-machine stator magnets proximate the rotors, a drive train connecting the output or input of the plurality of electric sub- machine rotors to simultaneously drive, or be driven by, the primary output or input shaft. The electric machine is preferably an electric motor, in which case it preferably comprises: a primary mechanical output, a plurality of electric sub-motor rotors, a plurality of electric sub- motor stator magnets proximate the rotors, a drive train connecting the outputs of the plurality of electric sub-machine rotors to simultaneously drive a primary output shaft.

The motor according to the present invention is intended to replace a conventional, single rotor electric motor.

Preferably at least two of the plurality of rotors share a common stator magnet. This is beneficial in reducing the amount of magnetic material required, which in turn reduces the cost and weight of the actuator. If the stators are electromagnets, copper winding material and electricity in powering them. More than one rotor can be arranged on a single shaft, the rotors having individual stators, or a pair of unitary stators running the length of the shaft, resulting in a long, thin rotor arrangement. A benefit of driving a single shaft with more than one rotor is that the number of gears is reduced.

Each rotor arrangement may be provided in layers, stacked on top of each other and using common shafts spanning the layers. This also reduces the number of gears required. The commutators for such a system may be combined or stacked.

Preferably the motor comprises at least 3 rotors, each of which shares a stator magnet with an adjacent rotor. Preferably each rotor is configured to rotate in the same rotational direction in use. This allows each output to drive a common primary output gear.

Alternatively, the motor may comprise a plurality of separate electric sub-motors, each comprising individual rotors and stators. In this way, the invention can be manufactured using a number of “off the shelf’ sub-motors.

Preferably the motor comprises at least 3 separate electric sub-motors.

The provision of a plurality of electric sub-motor rotors in order to provide the required output has many advantages over the prior art, including a significant saving in the weight of the motor, as well as the weight of a gear box, which can be constructed from more lightweight material due to the division of the total output torque required across the number of sub-motors installed (e.g. six sub-motors would each provide one sixth of the torque etc). Therefore e.g. plastics materials may be used where metals were previously required.

Preferably the drive train comprises a substantially identical gear assembly for each of the plurality of sub-motors, each gear assembly configured to gear the output of the respective sub-motor, and each gear assembly engaged with a primary output gear connected to the primary output shaft.

The gear assemblies may be engaged with the primary output gear at equally spaced positions around the primary output gear. This results in a mechanically balanced output, reduced noise and wear on the rotor bearings or bushes.

The primary output gear is preferably fixed for rotation with the primary output shaft. Each gear assembly may comprise at least: an initial stage configured to gear the output from the respective sub-motor, a first intermediate stage configured to gear the output from the first stage, and, a final stage configured to engage the primary output gear. Each gear assembly may comprise a second intermediate stage between the first intermediate stage and the final stage. This allows even higher gear ratios. It is advantageous because smaller electric motors tend to run optimally at higher speeds.

Preferably the initial stage and the second intermediate stage are coaxially aligned, and preferably the initial stage and the second intermediate stage are mounted on a first common shaft and are arranged to contra-rotate on the first common shaft.

The first intermediate stage and the final stage may be coaxially aligned. Preferably the first intermediate stage and the final stage are mounted on a second common shaft and are arranged to contra-rotate on the second common shaft.

By aligning gear stages on a common shaft and allowing them to contra-rotate, the shaft becomes less prone to noise, vibration and high forces in use as it is stabilised by the contra-rotating action.

Due to the reduced (split) torque on the gear arrangements, the drive train may comprise gears constructed from a plastics material in certain applications.

The following is an example of the benefits of a multi-core motor compared to a single-core motor and as such these benefits are apparent in electric machines constructed in accordance with the first to fourth aspects of the invention.

A traditional brushed or brushless electric motor of a known actuator may run at 12V DC at 3 A, providing (for example) 60 mNm of output torque at 6000 rpm (628 rad/s). This may be referred to as original motor A "OM-A". Such gear boxes are known in the art and reduce the speed by a factor of 2000 whilst increasing the torque by the same factor. Such a combined actuator and gear box will be referred to as original motor system "OMS-A". In OMS-A, losses through the gear box may be assumed to be 1 to 2% of the total output. The present invention breaks the single OM-A motor, referenced above, into a plurality, e.g. six individual, smaller sub-motors with the aim of producing the same mechanical output. The composite motor is known as CNM-A. If the rotor coil of the above referenced motor is split into sub-motors having six equal parts, each new individual sub-motor would provide 10 mNm at 6000 rpm (one-sixth of the output torque at the same speed). By summing the output torques at the same speed, the same output as the original single motor system OM-A described above, would be provided.

It will be noted that each new smaller sub-motor (which we will referred to as NM- 1 to NM-6) will each only be required to carry one-sixth of the current, that is 0.5A at 12V DC. It will also be noted that the rotor wire needs only to be one- sixth of the thickness in order to carry this smaller current. As such, the amount of wire mass required for the six individual sub-motors compared with the original motor OM-A is approximately 80% less (i.e. only 20% or one fifth of the original wire mass).

Because the power requirement of each sub-motor is relatively low, the magnetic flux across the sub-motor coil is also lower than the equivalent single rotor motor. In other words, each of NM-1 to NM6 requires one sixth of the flux (and thus one sixth of the magnetised material).

In addition, the rotor of NM-1 to NM-6 is much smaller than OM-A. Therefore, the gap required between the stators in order to surround the rotor of each sub-motor is reduced. As such as well as requiring one sixth of the flux, each motor only requires it to be established across a smaller gap. This leads to a further benefit, by an inverse square law relative to the amount of magnetic material required. Therefore, each of NM-1 to NM-6 requires less than one-sixth of the magnetic material in OM-A. In reality, the approximate size and weight reduction of the total magnet mass is approximately 80%. In a similar system which utilises electro-magnets to establish the magnetic field of the stator, a similar power reduction into the stator coils would also be realised. This is because the strength of the magnetic field is dependent upon the power within the electromagnetic coil, and the air gap, both of which can be reduced for smaller motors.

Turning to Figure 1, various combinations of motors are shown in tabular form. The columns are as follows:

Column A Number of sub-motors Column B Potential difference across each sub -motor input Column C Current used per sub-motor Column D Output torque per sub-motor Column E Summed output torque Column F Percentage copper saving on rotor wire material Column G Percentage saving on magnetic material in stators.

Because the diameter of the rotor wire decreases the smaller the rotor is, the cross- sectional area also decreases and hence the amount of copper required.

The total torque output is always 60Nm (at the same speed for each arrangement). With the reduction in current comes the associated reduction in core wire diameter, and an associated reduction in cross sectional area in mm ² (which is proportional to the copper mass used). The final column represents the reduction in copper material required. The present example uses 6 motors and as such realises a reduction of about 80%.

An additional benefit of the composite motor is that the reduction of current in each sub-motor NM-1 to NM-6 means that, where NM-1 to NM-6 have brushes, the brushes can be made from steel, rather than carbon, which in part results in a much longer life of the motor. For example, a typical steel brush small motor of the above type will last approximately 875 hours compared to OM-A which may only last 500 hours. Small rotors have a high start-up torque and larger rotors have a lower star-up torque but a comparatively high running torque at low speed. A further benefit of the present invention is to provide both a high speed and a high torque from the same unit. Stall speed is also improved.

Preferably, the plurality of electric sub-motors comprises brushless DC (BLDC) motors. Preferably the plurality of electric sub-motors comprises at least 4 to 6 motors, more preferably 6 (although any number is envisaged including 8 motors). As can be seen from Figure 1, the benefit in terms of copper saving becomes less as the number of motors increases. 6 sub-motors are a good compromise between this saving and complexity/cost of manufacture.

Each gear assembly, or drive train is only required to handle one-sixth of the torque of the original prior art motor design and, as such, each of the gears can be constructed from light-weight, low-strength materials such as plastics materials. It will be noted that only the final output gear and shaft needs to be able to carry the entire torque output of the system. Therefore, the primary output gear may also be constructed from a plastic material.

This results in a significant weight saving and manufacturing cost saving over the prior art systems, which typically require metal gears.

An experiment on a known industrial ball valve results in a known single-core motor (24V, 0.6A) turning the valve through 90 degrees (from an open to a shut position) in 16 seconds. Using six smaller sub-motors with the same total power requirement (24V, 0.6A) turns the same valve in 3 seconds. This is a clear energy saving of around 80%.

Further benefits in materials saving can be seen by using common stators for sets of rotors. For example, a single permanent magnet stator positioned between two rotors may replace two such stators.

Turning to Figure 3a, the characteristics of a known electric motor OM-A are shown. The x-axis represents output torque (T), and the y-axis represents either current (A), speed (S), output power (P) or efficiency percentage (E). Known motors are usually run at maximum power (P) - i.e. around point PI in Figure 3a because it provides the best power- weight ratio. As will be noted, the efficiency E is far from the maximum possible. Operating at maximum efficiency (point P2) will not provide a beneficial power to weight ratio. Turning to Figure 3b, the characteristic of CNM-A is shown. The x-axis scale is the same. As a result of the above-mentioned weight saving by splitting the motor into several sub- motors, each motor NM-1 to NM-6 can be over specified. The additional mass from overspecification of the motors would not be problematic as it is offset by the aforementioned savings. By over specifying the motors, each can be run nearer to its peak efficiency, whilst providing an improved power to weight ratio over OM-A (i.e. run at point P3).

It will be noted that the starting efficiency of the composite motor CNM-A in Figure 3b is not as high as the eventual running efficiency. To run CNM-A across a broad range of speeds, the invention according to the first to fourth aspects can be employed. This is shown in Figure 3c.

As the composite motor CNM-A starts, only one of the sub-motors NM-1 is engaged to drive the output (the remaining motors are preferably disengaged electromagnetically). As the power (P) of the composite motor CNM-A increases past a first threshold Tl, a second sub-motor NM-2 is engaged. The first threshold Tl is at the point where the efficiency (E) of a single motor is about to drop off, and as such the addition of a second motor NM-2 "stretches" the efficiency curve. Again, the efficiency of two motors will eventually drop off, and at threshold T3, a third sub-motor NM-3 is engaged, and so on. In this manner, the efficiency of the composite motor CNM-A is kept at a high level, and also relatively constant across the operating range. As such, CNM-A can be run across a large range of powers with high efficiency, unlike known motor OM-A.

The invention according to the first to seventh aspects is suitable for use in a range of applications.

According to the invention there is provided a fluid pump comprising a motor according to one of the first to fourth aspects. The pump may be a liquid pump in the domestic, commercial or industrial field, for example: pumps in heating systems, fuel pumping systems, pumps for swimming pools, pressure pumps in fire engines, hoses and fountains, pumps in drinks coolers and ice making machines, pumps in oil refineries, chemical, pharmaceutical & power generating plants, pumps in drinks manufacturing, pumps in refrigeration and freezer systems, pumps in ships / boats / submarines, pumps in water cooling systems, cooling towers, server room temperature control, pumps in mines for de-watering or similar, pumps in de-salination plants, reverse osmosis plants, pumps in breweries, distilleries, bottling plants, pumps in the utility water industry, waste water treatment and sewage treatment, filtration systems i7n the water industry, and pumps in pressure washers and showers.

The pump may be a gas pump in the domestic, commercial or industrial field, for example: pumps for air conditioning units, exhaust pumps/ fans in mines, air circulation fans, extraction fans, gas circulation units in the gas industry, gas circulation units in liquid bottling plants, motors in compressors, and domestic, commercial and industrial ventilation systems.

According to the invention there is provided a conveyor comprising a motor according to at least one of the first to fourth aspects. The conveyor may be employed in, for example: industrial conveyor belts, baggage handling systems, baggage carousel (airport), freight handling systems, moving walkways, pedestrian walkways, residential stair lifts, ski chair lifts, escalators, vehicle loading ramps, wheelchairs and mobile chairs, and mobile seating in lecture theatres and sports arenas.

According to the invention there is provided an aircraft system comprising a motor according to one of the first to fourth aspects. The system may be employed in, for example: helicopter rotor drive motors, propeller motors, flaps and control surfaces, landing gear deployment, remote control aeroplane or helicopter motors, aeroplane or helicopter doors, aeroplane extending entry ramps, cargo bay doors, loading ramps, and microlite aircraft.

According to the invention there is provided an aerospace system comprising a motor according to at least one of the first to fourth aspects. The system may be employed in, for example: large crawler systems for transporting heavy items, systems for unfurling solar panels, control systems for telescopes or other instrumentation, air recycling systems, environmental control systems, cargo doors, robotic arms and booms, and, assisted movement in spacesuits.

According to the invention there is provided a domestic, commercial or industrial appliance comprising a motor according to at least one of the first to fourth aspects. The appliance may be, for example: a blender, a fridge, a freezer, a dish / glass washer, a tumble dryer, a washing machine, a microwave, a toaster, a rotary oven, a spit roasting machine, a hand drier, a hair dryer, or, a power tool.

According to the invention there is provided a fairground or theme park ride comprising a motor according to at least one of the first to fourth aspects. The ride may be, for example: a carousel, a ferris wheel, a roller coaster, or, dodgems. According to the invention there is plant machinery comprising a motor according to at least one of the first to fourth aspects. The machinery may be, for example: grader systems for roads, digger scoops and arms, dumper tipping systems, cement mixer mobile, or, cement mixer vehicle based.

According to the invention there is provided a vehicle comprising a motor according to at least one of the first to fourth aspects used as a drive source. The vehicle may be, for example wheel hub or engine replacement / hybrid system or used as a starter motor.

The vehicle may be a car or truck for example, or a hybrid train.

Brief Description of the Drawings.

The foregoing and further features of the present invention will be apparent from the following description of preferred embodiments which are provided by way of example only in connection with the accompanying figures, of which:

FIGURE 1 is a table showing savings in the electric machine materials of the present invention;

FIGURE 2 is a graph of a statistic from Figure 1 ;

FIGURES 3a to 3c are motor performance graphs;

FIGURE 4a is a schematic underside view of a part of a first electric machine in accordance with the present invention;

FIGURE 4b is an underside schematic view of the electric machine of Figure 1 showing a casing;

FIGURE 4c is a side view of the electric machine of Figure 1 ;

FIGURE 5 is an end on cross-sectional view of an electric sub-machine for the electric machine of Figure 1 ;

FIGURE 6 is an electrical commutation diagram for a BLDC motor;

FIGURE 7 is a schematic view of a part of a second electric machine in accordance with the present invention;

FIGURE 8 is a schematic view of a part the electric machine of Figure 5;

FIGURE 9 is a schematic view of a part of a third electric machine in accordance with the present invention;

FIGURE 10 is a schematic view of a part of a fourth electric machine in accordance with the present invention;

FIGURE 11 is a schematic view of a part of a fifth electric machine in accordance with the present invention; FIGURE 12 is a schematic view of a part of a sixth electric machine in accordance with the present invention;

FIGURE 12a is a schematic view of a part of a seventh electric machine in accordance with the present invention;

FIGURE 13 is a schematic view of a part of an eighth electric machine in accordance with the present invention;

FIGURE 14 is a schematic view of a ninth electric machine in accordance with the present invention;

FIGURE 15 is a schematic view of a tenth electric machine in accordance with the present invention;

FIGURE 16 is a schematic view of an eleventh electric machine in accordance with the present invention;

FIGURE 17 is a flowchart of a design process for the present invention;

FIGURE 18 is a schematic of a control system for an electric machine in accordance with the present invention;

FIGURE 19 is a schematic view of a primary mechanical output for another embodiment of an electric machine in accordance with the invention;

FIGURE 20 is a schematic view of output gear indexing for the embodiment of the electric machine of Figure 19;

FIGURE 21 is a Hall effect transition diagram for the embodiment of the electric machine of Figure 19;

FIGURE 22 is a Hall effect transition diagram for another embodiment of an electric machine in accordance with the invention;

FIGURE 23 is a schematic view of a pump assembly comprising a motor according to the present invention;

FIGURE 24 is a schematic view of a washing machine comprising a motor according to the present invention;

FIGURE 25 is a schematic view of a car comprising a motor according to the present invention;

FIGURE 26 is a schematic view of a part of the car of Figure 25;

FIGURE 27 is a schematic view of a vehicle comprising one or more electric machines according to the present invention;

FIGURE 28 is a table showing savings in the core wire of cables used in the present invention; FIGURE 29 is a schematic view of another vehicle comprising one or more electric machines according to the present invention;

FIGURE 30 is a schematic view of yet another vehicle comprising one or more electric machines according to the present invention;

FIGURE 31 is a stripped-down perspective view of an embodiment of an electric machine in accordance with the invention;

FIGURE 32 is a perspective view of a vehicle axel including the electric machine of Figure 31 ;

FIGURE 33 is a perspective view of the vehicle axel including the electric machine of Figure 31 in an alternative orientation.

Description of Preferred Embodiments.

The following description is of preferred embodiments by way of example only and without limitation to the combination of features necessary for carrying the invention into effect.

Reference in this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Moreover, various features are described which may be exhibited by some embodiments and not by others. Similarly, various requirements are described which may be requirements for some embodiments, but not other embodiments.

It should be understood that the elements shown in the FIGS, may be implemented in various forms of hardware, software or combinations thereof. These elements may be implemented in a combination of hardware and software on one or more appropriately programmed general-purpose devices, which may include a processor, memory and input/output interfaces.

The present description illustrates the principles of the present invention. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the invention and are included within its spirit and scope.

Moreover, all statements herein reciting principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure.

Thus, for example, it will be appreciated by those skilled in the art that the block diagrams presented herein represent conceptual views of systems and devices embodying the principles of the invention.

The functions of the various elements shown in the figures may be provided through the use of dedicated hardware as well as hardware capable of executing software in association with appropriate software. When provided by a processor, the functions may be provided by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some of which may be shared. Moreover, explicit use of the term "processor" or "controller" should not be construed to refer exclusively to hardware capable of executing software, and may implicitly include, without limitation, digital signal processor ("DSP") hardware, read-only memory ("ROM") for storing software, random access memory ("RAM"), and non-volatile storage.

Turning to Figure 4a, a motor 100 preferably comprises six electric sub-motors 102, although more or less electric sub-motors may be deployed depending on the use to which the motor 100 is put. There is, however at least two electric sub-motors as a minimum. Preferably, the electric sub-motors 102 are BLDC motors.

Each electric sub-motor 102 has an output shaft 104 on which a motor output gear 106 is mounted. The output shaft 104 and motor output gear 106 share a motor axis 108 (see Figure 4c). Parallel to and offset from the motor axis 108, a first gear assembly 110 is provided having an input gear 112 of diameter Dl, connected by a shaft 114 to an output gear 116 having a diameter D2. The gears 112, 116 and the shaft 114 are mounted to rotate about a first gear assembly axis 118. A second gear assembly 120 is provided, having an input gear 122 having a diameter D3 connected by a shaft 124 to an output gear 126 having a diameter D4. The gears 122, 126 and the shaft 124 are mounted to rotate about a second gear assembly axis 128.

The third gear assembly 130 is provided comprising an input gear 132 having a diameter D5, connected by a shaft 134 to an output gear 136 having a diameter D6. The gears 132, 136 and the shaft 134 are mounted to rotate about a third gear assembly axis 138. A fourth gear assembly 140 is provided having an input gear 142 having a diameter D7, connected by a shaft 144 to an output gear 146 having a diameter D8. The gears 142, 146 and shaft 144 are arranged to rotate about a fourth gear assembly axis 148. The motor 100 comprises a primary output gear 150 connected to an output shaft 152 for rotation about an output axis 154. In use, the axis 108, 118, 128, 138, 148, 154 are all parallel. The gear assemblies 110, 120, 130, 140 successively form a drive train between the electric sub-motor 102 and the output shaft 152. As such, the motor output gear 106 is engaged for rotation with the input gear 112 of the first gear assembly 110. The output gear 116 of the first gear assembly 110 is engaged for rotation with the input gear 112 of the second gear assembly 120. The output gear 126 of the second gear assembly 120 is engaged for rotation with the input gear 132 of the third gear assembly 130. The output gear of the third gear assembly 130 is engaged for rotation with the input gear 142 of the fourth gear assembly 140. The output gear 146 of the fourth gear assembly 140 is engaged for rotation with the primary output gear 150 of the motor 100.

Due to the fact that each of the input gears 112, 122, 132, 142 each has a larger diameter (Dl, D3, D5, D7 respectively) than the output gears 116, 126, 136, 146 (D2, D4, D6, D8 respectively) the gear chain steps down the speed of the electric sub- motor 102 and consequently increases the torque thereof such that the input at the primary output gear 150 is of a relatively low speed and high torque compared to the output shaft 104 of the sub motor 102.

By making the input gears 112, 122, 132, 142 the same diameter (D1=D3=D5=D7), and the output gears 116, 126, 136, the same diameter (D2=D4=D6) the alternate gear assemblies 110, 130 can be stacked on top of each other and coaxial (i.e. axes 118 and 138 align). Alternate gear assemblies 120, 140 are also stacked and coaxial (i.e. axes 128 and 148 align). This makes the gear train more compact. Referring back to Figure 4a, six such assemblies are provided comprising six electric sub-motors 102, preferably equally spaced around the output axis 154 of the motor. As such, each of the output gears 146 of the gear chains engages in a different position around the circumference of the output gear 150 such that the forces applied to the output gear 150 are cumulative across each of the six sub motors 102.

Referring to Figure 4b, the entire assembly is placed within a compact housing 156 in which the series of individual sub-motors may comprise “off the shelf’ BLDC motors.

Referring again to Figure 4c, the BLDC electric sub-motor 102 has a rotor 158 which may be a permanent magnet rotor. In this embodiment, the rotor 158 is surrounded by a stator 160 comprising a plurality of stator windings 161 (Figure 5). However, it will be understood that the principles described herein apply equally to BLDC electric sub-motors having an internal stator surrounded by an external rotor as is commonly found in BLDC motors for self-balancing scooters and the like.

In the motor 100 of Figure 4c, at least one and preferably at least two of the electric sub-motors includes a rotor position detector device 162. The rotor position detector device 162 preferably comprises at least one Hall effect sensor 164 and, in some embodiments comprises three such Hall effect sensors 164 as best seen in Figure 5 which shows an end view of an electric sub-motor 102. The three Hall effect sensors are preferably embedded in the stator rotationally separated by 120 degrees, although this is not essential. It will be understood that any suitable rotor position detector device or system may be employed in the invention.

Typically, in a BLDC motor such as any of the electric sub-motors 102, the stator windings 161 are energized in a certain sequence with typically one winding being positive, one winding being negative, and the third winding being powered off. Torque production is caused by the attraction and repulsion between the stator field and the permanent/electro magnets of the rotor. Maximum torque is achieved when these two fields are orientated at 90 degrees to each other, and torque diminishes as the fields align. Therefore, in order to keep the motor turning, the stator’ s magnetic field changes position as the rotor field “catches up” with it.

In order to energize the correct stator winding at the correct or most efficient time, the rotor position must be known. Rotor position is detected by the one or more Hall effect sensors 164 which monitor or detect the rotor’s position, i.e. monitor or detect the rotor’s pole positions. BLDC motors typically have three Hall effect sensors mounted either to the stator as shown or to the rotor and use what is known as six-step electrical commutation as shown in Figure 6. When a rotor pole passes a sensor 164, it produces either a high or a low signal to indicate which rotor pole (N or S) has passed. This switching of the three hall effect sensors 164 from high to low or from low to high provides rotor position information every 60 degrees. As shown in Figure 6, in six-step electrical commutation, each of the three windings (U, V, W) is either energized positive, negative, or off, depending on whether each of the three Hall effect sensors 164 (HI, H2, H3) has a high or a low state. Consequently, in this arrangement, the electrical commutation occurs in 60-degree segments. Whilst this is sufficient for controlling continuous operation of the electric sub-motor 102, it creates a problem on initial start-up of the electric sub-motor.

At initial start-up, the initial rotor position based on a detected pole of the rotor is only known within one of the sixty degree segments, i.e. there is an error margin of up to 60 degrees in the assumed initial position of the rotor, because, when rotor is stationary, the Hall effect sensors 164 in this embodiment are accurate to only 60 degrees. There is a need therefore to obtain a more accurate estimate of the position of the rotor 158 to enable a faster and more efficient start-up phase for the electric sub-motors 102. This is particularly desirable for stop-start motors, i.e. motors which are repeatedly being started and stopped in quick succession.

Figures 7 to 13 show an alternative architecture for the electric machine of the present invention, which instead of utilising a series of individual motors (which can be obtained “off the shelf’), a custom-built motor can be provided in a single housing.

Referring to figures 7 and 8, a motor 300 comprises a first permanent magnet stator 302, a second permanent magnet stator 304 and a third permanent magnet stator 306. Each of the stators is aligned with North-South (NS) orientation the same.

A first electric motor rotor 308 is positioned for rotation between the North and South poles of the first and second stators 302, 304 respectively and comprises a shaft 310, a terminal 312 for connection to an electricity supply (e.g. a commutator in a brushed motor), a core 314 and windings 316. The shaft is connected to an output gear 318.

A second electric motor rotor 320 is positioned between the North and South poles of the second and third stators 304, 306 respectively. It is substantially identical to the first rotor 308.

The output gears 318 of the rotors 308, 320 can be summed with a gear train per the earlier embodiments of the invention. A primary output gear 322 is shown for exemplary purposes, but it will be understood that a gear arrangement with a much higher ratio may be provided.

Turning to Figure 9, a further example is shown in which a motor 400 comprises a central stator 402 surrounded by a first rotor 404, a second rotor 406 and a third rotor 408. Each rotor is provided with a peripheral stator 410, 412, 414 respectively which has a pole opposite to the outer face of the central stator. Each rotor 404, 406, 408 has an output gear 416, 418, 420 meshed with an example gear train in the form of a primary output gear 422. Figures 10 and 11 show alternative arrangements for four rotors. The motor 500 of Figure 10 has a central stator 502 with four rotors 504, 506, 508, 510 positioned in two pairs either side thereof. A first pair of rotors 504, 508 is provided with a first common peripheral stator 512, and a second pair of rotors 506, 510 is provided with a second common peripheral stator 514. Figure 11 shows a similar motor 600, but four rotors 602, 604, 606, 608 are evenly spaced at 90 degrees around a common stator 610, and each rotor 602, 604, 606, 608 has its own respective peripheral stator 612, 614, 616, 618 respectively. Figures 12 and 13 show the equivalent motors to figures 10 and 11 but with six rotors instead of four.

Figures 10 and 11 show alternative arrangements for four rotors. The motor 700 of Figure 10 has a central stator 702 with six rotors 701, 703, 704, 705, 706, 707 positioned in two sets of three either side thereof. A first set of rotors 701, 703, 704 is provided with a first common peripheral stator 712, and a second set of rotors 705, 706, 707 is provided with a second common peripheral stator 714.

Figure 12a shows a similar motor 800 to the motor 700, but six rotors 801, 802, 803, 804, 805, 806 are evenly spaced at 60 degrees around a common stator 807, and each rotor 801, 802, 803, 804, 805, 806 has its own respective peripheral stator 808, 809, 810, 811, 812, 813 respectively.

Turning to Figure 13, a two-layer motor 900 is shown having a first layer 902 and a second layer 904, each equivalent to the motor 300. The first layer 902 has a first, second and third stator 906, 908, 910 with two rotors 912, 914 interspersed therebetween. Similarly, the second layer 904 has a first, second and third stator 916, 918, 920 with two rotors 922, 924 interspersed therebetween. The rotors 912, 922 are mounted on a common shaft 926 having a multiple commutator 928 at a first end, and an output gear 930 at a second end. Similarly, the rotors 914, 924 are mounted on a common shaft 932 having a multiple commutator 934 at a first end, and an output gear 934 at a second end.

The gears 930, 936 are engaged with a primary output gear 938.

In the example of Figure 13, the shafts 926, 932 are integral, although the rotors on each shaft may be arranged to rotate relative to one another, or even counter rotate (by appropriately reversing the rotor windings or stator magnetic orientation) to provide a balancing effect.

Advantageously, stacking the rotor sets reduces the number of gears and commutators for a given motor assembly. Further layers can be added if required, such that the motor shape can be constructed to fill the packaging space available.

Figures 14 to 16 show various methods for engaging and disengaging the sub-motors or sub-generators. Each will be described with reference to a motor, but it will be appreciated that the apparatus and method described is equally applicable to generators. The general apparatus and methods of Figures 14 to 16 are applicable to each of the above-described electric machines. Turning to Figure 14, a composite motor 3000 comprises a first and second sub motor 3002, 3004 respectively. Two sub-motors 3002, 3004 are shown for simplicity, but further sub-motors may be present in accordance with the above-described embodiments.

Each motor 3002, 3004 has a respective output shaft 3006, 3008, with a respective output gear 3010, 3012. The gears 3010, 3012 are axially slidable on the shafts 3006, 3008 but rotationally fixed therewith (e.g. by a spline). The gears 3010, 3012 are meshed with a primary output gear 3014, which in turn drives a primary output shaft 3016. The motor 3000 comprises an actuation system for moving the gears 3010, 3012 axially along the shafts 3006, 3008 into and out of engagement with the primary output gear 3014 in accordance with the operating principles described below.

Turning to Figure 15, a composite motor 3100 comprises a first and second sub motor 3102, 3104 respectively. Two sub-motors 3102, 3104 are shown for simplicity, but further sub-motors may be present in accordance with the above-described embodiments.

Each motor 3102, 3104 has a respective output shaft 3106, 3108. A clutch 3116, 3118 is provided on each shaft 3106, 3108 to selectively interrupt transmission. Each clutch has an output shaft 3120, 3122 with a respective output gear 3110, 30123112.

The gears 3110, 31123012 are meshed with a primary output gear , which in turn drives a primary output shaft 30163126. The clutches 3116, 3118 can therefore be used to selectively engage and disengage the motors 3102, 3104 from driving the primary output shaft 31 163126.

A further composite motor 3200 is shown in Figure 16. The motor 3200 comprises a primary output shaft 3202 having a first second and third permanent magnet rotor 3204, 3206, 3208. The first rotor 3204 is provided with a first stator part 3210 and a second stator part 3212. The second rotor 3206 is provided with a third stator part 3214 and a fourth stator part 3216. The third rotor 3208 is provided with a fifth stator part 3218 and a sixth stator part 3220. Each respective pair of stators is provided as an electromagnet, thus forming three brushless motors on the shaft 3202. The stator pairs are mounted to actuation assemblies- e.g. assemblies 3222 and 3224. The actuation assemblies can retract and deploy the stator pairs to take them away from, or closer to, the rotor 3204. As such, each sub-motor can be disengaged. It will be noted that each sub-rotor could be disengaged by disconnecting the power supply to the stator. Although this would provide some limited functionality, the rotor magnet would establish an alternating current in the stator coils, and thus would experience some resistance, which is undesirable. Taking the stators away from the magnetic field of the rotor mitigates this effect. A composite electric machine in accordance with Figures 14 to 16 is designed in accordance with Figure 17.

Firstly, the power requirement, Preq, of the composite machine is established at step S4000. This is usually the maximum mechanical power which is likely to be delivered by a composite motor, or the maximum electrical power which is likely to be delivered by a composite generator.

At step S4002, the number of sub-machines, N, is chosen (for example 6).

At step S4004, n identical electric machines are specified. Individual machines are typically rated at their maximum power output (which with reference to Figure 3 a is not at their maximum efficiency). Instead of using n machines each having maximum power Preq/N, according to the invention the machines are over specified. That is, each sub machine is chosen to provide power Preq at peak efficiency- that is operating in the region of PI in Figure 3 a. It will be noted that the peak power of each submachine will exceed Preq/N by a factor of at least three.

Ideally, each machine will be specified such that operating at Preq/2N, it its operating at maximum efficiency to ensure that each motor has an operating range spanning the maximum efficiency. At step S4008, the controller parameters are specified (control will be discussed in more detail below). The controller is connected to a sensor measuring a parameter indicative of the operating power of the machine. It is configured to engage 1 electric machine from zero power to Preq/N, two machines at 2*Preq/N, three machines at 3*Preq/N and so on until n=N machines at power Preq.

The invention also provides a controller and method of operating a composite electric machine which is configured to allow selective disengagement of its constituent sub- motors.

A composite electric machine 200 comprising a controller according to the present invention is shown in Figure 18. The machine 5000 comprises three sub-machines 5002, 5004, 5006 driving, or being driven by (depending on whether the machine 5000 is a motor or generator) a primary shaft 5008 as described above.

Each sub-machine can be individually and selectively disengaged from the shaft 5008 by a controller 5010. The controller 5010 may, for example, be configured to disengage a clutch in the sub-machines 5002, 5004, 5006.

Each sub-machine 5002, 5004, 5006 is connected to an electrical power storage unit 5012 by power lines 5014, 5016, 5018. Electrical power sensors 5020, 5022, 5024 are positioned in the power lines to measure the electrical power being converted by each sub machine 5002, 5004, 5006 respectively. Each sensor feeds back to the controller 5010. In use, the controller 5010 can thereby monitor the electrical power being converted by the composite machine 5000 and engage the required sub-machine in order to maintain high efficiency in accordance with Figure 3c.

The controller 5010, which comprises control software running on a CPU with an associated memory, does not always engage the same sub-machines in the same order. In one embodiment, the controller 5010 will engage alternate sub-machines as the first sub machine. For example, in the first use of the machine 5000, sub-machine 5002 may be engaged first, later supplemented by machines 5004, 5006. In another embodiment, the controller 5010 retains a work history for each submachine on its memory. The controller will select the next sub-machine to be engaged depending on its work history, in order to encourage even use of all sub- machines. The sub-machine with the least use will be engaged next. The controller 5010 does not always disengage the sub-machines in order. Instead, if the controller 5010 needs to disengage a sub-machine based on a drop in machine power, it will disengage the sub-machine with the highest use.

It will be understood that the controller 200 can control any number of sub-machines such as the electric sub-motors 102 of Figures 4a to 4c. The controller 200 may also be configured to control said electric sub-motors 102 based on rotor position signals received from said one or more rotor position detector devices 162.

In an embodiment of the motor 100 of Figures 4a to 4c where there are six electric sub-motors 102, although the number of electric sub-motors 102 may be more than or less than six depending on the motor 100 application, the resulting electric motor assembly is such that each of the electric sub-motors 102 can be assembled with the primary output gear 150 such that a rotor 158 of at least one of said electric sub-motors 102 has a known rotational positional relationship with the primary output gear 150/primary output shaft 152. This can be implemented in embodiments of motor 100 without or without a drive train between the electric sub-motor 102 and the primary output gear 150 or primary output shaft 152, i.e. where an output gear 106 of the electric sub-motor 102 is meshed either directly or indirectly via a drive train with said primary output gear 150. It will be understood that where the rotor 158 of an electric sub-motor 102 is assembled in the motor 100 such as to have a known rotational positional relationship with primary output gear 150/primary output shaft 152 then, by extension, the same known rotational positional relationship exists between both the output shaft 104 and the output gear 106 of the electric sub-motor 102 and the primary output gear 150/primary output shaft 152. In an embodiment of the motor 100 where each of the electric sub-motors 102 is assembled such that its rotor has a known rotational positional relationship with the primary output gear 150/primary output shaft 152, it is possible to provide only one of said electric sub-motors 102 with a rotor position detector device 162 and to use the signals from said rotor position detector device 162 in the controller to control motive operation of all of said electric sub-motors 102. This is because the rotor position signals from the only electric sub-motor 102 being provisioned with a rotor position detector device 162 can be applied to any other electric sub-motor 102 as the rotational positions of all of the rotors of the plurality of electric sub-motors 102 with respect to the primary output gear 150/primary output shaft 152 can be determined from their respective known rotor rotational positional relationships with the primary output gear 150/primary output shaft 152. This therefore simplifies control of the motor 100 and enables BLDC motors not having any rotor position detector device/system to be utilised as the electric sub-motors 102 save for one such motor which, in this embodiment, must have a rotor position detector device 162. Control of the motor 100 is simplified further in this embodiment when all of the electric sub -motors 102 are assembled with their rotors in a same rotational position with respect to the primary output gear 150/primary output shaft 152 because then the signals from the one rotor position detector device 162 are directly applicable to controlling each of said electric sub-motors.

In a more preferred embodiment of the motor 100 in accordance with the invention, it is preferred that at least two, but preferably more of the electric sub-motors 102 are each provided with a rotor position detector device 162 and where said at least two electric sub motors 102 each have a known rotational relationship with the primary output gear 150/primary output shaft 152. In this embodiment of the motor 100, at least one of said two or more electric sub-machines 102 has its rotor 158 rotationally offset by a set amount relative to a rotor 158 of at least one other of said two or more electric sub-machines 102.

By offsetting one of the rotors 158 of one of the electric sub-machines 102 by a set amount, i.e. a selected, predetermined or calculated rotational amount, with respect to the position of one of the other rotors 158 and knowing the respective rotational relationships of said rotors 158 with the primary output gear 150/primary output shaft 152, it means that it is possible to determine from the signals from the two or more rotor position detector device 162 an initial stationary position of each of said rotors 158 within a reduced rotational error amount compared to a conventional motor arrangement. This can be better understood when considering the situation where each of the rotors 158 has a same rotational positional relationship with the primary output gear 150/primary output shaft 152. In such a case, because of the relative alignment of the rotors 158, when all of the rotors 158 rotate, their respective rotor position detector devices 162 (Hall effect sensors 164) will switch in unison thereby providing no new information about any of the rotor initial stationary positions as all of said rotor position detector devices 162 will exhibit the same rotor initial position error range of 60 degrees, for example. However, when the rotors 158 are rotationally offset relative to each other within their known rotational positional relationships with the primary output gear 150/primary output shaft 152, the outputs of the rotor position detector devices 162 provide new information which enables a determination of a decreased rotor initial position error range because said rotor position detector devices 162 will exhibit overlapping rotor initial position error ranges.

It follows from the foregoing that a greater reduction in rotor initial position error range can be achieved if most or all of the electric sub-machines 102 are provided with rotor position detector devices 162 and have their rotors 158 rotationally offset by known amounts with respect to each other.

In one embodiment, at least half of said plurality of electric sub-motors 102 include a rotor position detector device 162 with its rotor 158 rotationally offset relative to rotors 158 of remaining ones of said electric sub-motors 102. More preferably, all of said plurality of electric sub -motors 102 include a rotor position detector device 162 with its rotor 158 rotationally offset relative to rotors 158 of remaining ones of said plurality of electric sub motors 102.

In this embodiment, initial rotor positions on start up for some or all of said plurality of electric sub-motors 102 are derived, extrapolated, or calculated from rotor position signals provided by said rotor position detector devices 162.

A rotor 158 of at least one of said plurality of electric sub-motors 102 may be rotationally offset by a set amount relative a rotor 158 of at least one other of said plurality of electric sub-motors 102 by indexing a mechanical output of said one of said plurality of electric sub-motors 102 with respect to the primary output gear 150.

Referring to Figure 18, shown is another embodiment of the motor 100 in accordance with the invention in which the primary output gear 150 of the motor 100 is directly meshed with respective output gears 106 of eight electric sub-motors 102 although, in another embodiment, the primary output gear 150 of the motor 100 is meshed with output gears 146 of drive trains connecting the output gears 106 of the eight electric sub-motors 102 with the primary output gear 150. In either case, as shown in Figure 19, it is possible to index different rotational offset positions for the rotors 158 of each of the eight electric sub-motors 102 by, for example, offsetting the pinion of the output gear 106 or the output gear 146 by one or more teeth.

In the embodiments illustrated by Figures 18 and 19, each output gear 106 or each output gear 146 has seventeen teeth. Where each of the eight electric sub-motors 102 has a rotor position detector device 162 comprising three Hall effect sensors 164 then Figure 20 illustrates the Hall effect transitions versus rotational angle for the eight rotor position detector devices 162. This provides a non-uniform pattern of Hall effect transitions, but, despite this, it enables the rotor initial position error range for each of the eight electric sub motors 102 to be substantially decreased. In Figure 20, the transitions marked “T” comprise the Hall effect transitions which would occur if all of the rotors 158 of the eight electric sub motors 102 had the same rotational alignment with the primary output gear 150.

If, in the embodiments illustrated by Figures 18 and 19, each output gear 106 or each output gear 146 is provisioned with an even number of teeth, for example, sixteen teeth, then Figure 21 illustrates the Hall effect transitions versus rotational angle for the eight rotor position detector devices 162. It can be seen that, in this embodiment, the Hall effect transitions are uniformly spaced by 7.5 degrees through one full rotation. The uniform set of Hall effect transitions, i.e. rotor pole transitions, enables the controller algorithm to be substantially simplified with very accurate initial rotor starting positions. Again, the transitions marked “T” comprise the Hall effect transitions which would occur if all of the rotors 158 of the eight electric sub-motors 102 had the same rotational alignment with the primary output gear 150.

The above described electric machines can be used in a variety of applications.

The application of the invention to a motor is particularly well suited to drive pumps in various applications. For positive displacement pumps such as gear pumps, gerotor pumps and the like, prior art motors tend to project from the rear of the pump housing. As shown in Figure 23, a positive displacement pump 1000 such as a gerotor has an inlet 1002 and an outlet 1004. A prior art motor 1006 (shown in hidden line) drives the pump through an input shaft 1008.

A motor 1010 according to the present invention is provided in place of the prior art motor, comprising a plurality of sub-motors 1012 connected to a gearbox 1014 which in turn drives the shaft 1008.

As can be seen, the provision of a motor according to the present invention provides a more compact arrangement. Because a number of smaller sub-motors are used, the system can be shorter and wider, which often better matches the footprint of the pump in use. Furthermore, the motor according to the present invention is more reliable because if one motor were to fail, the remaining motors would carry on. This is equally applicable to impeller-type pumps such as axial flow or centrifugal pumps.

In situations where it is beneficial to reduce the axial length of an assembly, the present invention is particularly well suited. For example, in a domestic washing machine or tumble dryer it is beneficial to use as much axial space as possible for the drum.

Referring to Figure 24 a washing machine 1100 generally comprises a housing 1102 containing a stationary drum 1104 containing a rotating drum 1106 used to agitate and spin clothing during the washing cycle by rotating about an axis A.

In known machines, it is desirable to provide a drum 1106 which is as deep as possible to increase the load capacity. As such, known motors such as a motor 1108 as shown in Figure 24 are offset from the axis A and connected by a belt drive 1100. This is because the motor 1108 has to be large in order to provide the required torque and speed to spin the drum 1106.

A further problem with this arrangement is that the motor 1108 is off-centre and as such vibrations can occur which requires mass damping within the housing 1102. This makes the unit heavy and cumbersome.

A series of six sub-motors 1112 is provided according to the present invention and shown schematically in Figure 24. It will be understood that a gearbox will be required between the sub-motors 1112 and the drum 1106, but it can be seen that the present invention can be positioned about the rotation axis A whilst leaving sufficient space for the drum 1106.

This reduces the vibration caused by the offset mass of the motor 1108, reducing the need for damping. It also provides a quieter and more efficient product as the belt drive can be eliminated. It also allows the unit to be made more compact (if required).

Turning to Figure 25, a hybrid car 1200 is shown having an internal combustion engine 1202 which drives wheels 1204, 1206, 1208, 1210. An example wheel 1204 is shown in Figure 26 driven by a shaft 1212 from the engine 1202. As described, the car 1200 is a hybrid, and can be driven using power from a battery 1214. The battery 1214 is connected to a wheel motor 1216 comprising six individual motor cores 1218 and a gearbox 1220 which engages with the shaft 1212. The motor 1216 is configured in accordance with the present invention and the six motors provide a combined drive to the shaft 1212 to rotate the wheel 1204.

It will be noted that as a hybrid, when the shaft 1212 is driven by the engine 1202, the motor 1216 can be back driven to power and charge the battery 1214. As can be seen in Figure 26, the individual sub-motors 1218 can be positioned around the shaft 1212 and even within the wheel 1204 to provide a very compact arrangement which has minimum impact on vehicle packaging space.

Whilst car 1200 has been described as a hybrid car, it will be understood that it could be a fully electrically driven car, i.e. not including an internal combustion engine unit.

Figure 27 shows an electric vehicle 1300 which may be a fully electrically powered vehicle or a hybrid vehicle as in Figures 25 and 26. The vehicle 1300 has a plurality of electric machines 1302, 1304, 1306 and 1308 for providing motive to propel the vehicle 1300. In one embodiment, the electric machines comprise traditional electric motors of any type commonly unitized in electric vehicles. The electric machines 1302, 1304, 1306 and 1308 may each be mounted near or in association with a wheel of the vehicle 1300 such that each of the electric machines 1302, 1304, 1306 and 1308 provides motive force to a respective wheel of the vehicle 1300. The electric machines 1302, 1304, 1306 and 1308 may be connected to their respective wheels via axels and gearboxes (now shown). The vehicle 1300 have one or more energy storing units 1310 such as batteries for powering the electric machines 1302, 1304, 1306 and 1308. Each electric machine 1302, 1304, 1306 and 1308 has a motor controller 1312, 1314, 1316 and 1318. The motor controllers 1312, 1314, 1316 and 1318 are preferably mounted close to their respective electric machines 1302, 1304, 1306 and 1308. The motor controllers 1312, 1314, 1316 and 1318 may be mounted in endcaps or housings of said electric machines 1302, 1304, 1306 and 1308. A master motor controller 1320 may be provided to control the plurality of motor controllers 1312, 1314, 1316 and 1318, although this is not essential.

Take by way of example an electric vehicle powered by a single electric motor of a conventional motor type controlled by a single motor controller with a single set of power cables connecting a battery power supply to the single motor controller and the single electric motor with the system running a continuous current of 1000A at a voltage of 48V. In this example, the power output would be 48,000W (about 64 horsepower). The components in the motor controller would have to be able to handle a continuous current of 1000A. This would require very specialised components and power cables as well as any cable connectors or the like at very high cost.

For the vehicle 1300 of Figure 27, for a same output power of 48KW at 48V, the components of each motor controller 1312, 1314, 1316 and 1318 would only need to carry 250A, a very substantial reduction over the above example. If, in addition to using multiple electrical machines 1302, 1304, 1306 and 1308 with respective motor controllers 1312, 1314, 1316 and 1318, the vehicle 1300 was arranged such that a wiring loom 1311 comprising cables carrying power from the one or more energy storing units 1310 to the motor controllers 1312, 1314, 1316 and 1318 and the electrical machines 1302, 1304, 1306 and 1308 were arranged as respective cable circuits 1322, 1324, 1326 and 1328, then, compared to the example described above, it is possible to utilize cables of a significantly reduced thickness.

Figure 28 shows illustrates different example system where the total motor torque is 60Nm. Whilst this is at a lower scale than the above example, it serves to illustrate the point about the reduction in the cable (copper) thickness. Referring to Figure 28, it can be seen that, for a system comprising a single motor operating at a torque of 60Nm, the cable core thickness would be about 0.65mm. However, for a system comprising four electric motors each operating at 15Nm to provide a total torque of 60Nm, the cable core thickness for each motor would be about 0.36mm which represents a copper saving of 69%. The copper savings illustrated by Figure 28 hold true when the torque or power output of the electric motors is scaled up to the levels typical of electric vehicles.

For the vehicle of Figure 27, by using multiple electric machines 1302, 1304, 1306 and 1308 with respective wiring looms or cable circuits 1322, 1324, 1326 and 1328 extending from the one or more energy storing units 1310 to the motor controllers 1312, 1314, 1316 and 1318 and to the electrical machines 1302, 1304, 1306 and 1308 enables not only cables of smaller copper cores to be used, but, perhaps more usefully, it allows much less complex and much less expensive electrical and electronic components to be used in the motor controllers, for example.

Figure 29 shows an electric vehicle 1400 which may be a fully electrically powered vehicle or a hybrid vehicle as in Figures 25 and 26. The vehicle 1400 has one or more electric machines 1402, 1404, 1406 and 1408 in accordance with the invention, i.e. electric machines with multiple electric sub-machines configured to drive a primary mechanical output of the electric machine, the primary mechanical output for providing motive force to propel the vehicle 1400.

The electric machines 1402, 1404, 1406 and 1408 may each be mounted near or in association with a wheel of the vehicle 1400. The vehicle 1400 has one or more energy storing units 1410 such as batteries for powering the electric machines 1402, 1404, 1406 and 1408. In this embodiment, each electric machine 1402, 1404, 1406 and 1408 comprises ten electric sub-machines 1402’, 1404’, 1406’ and 1408’, although different numbers of electric sub-machines may be utilized in the electric machines for different vehicles or applications. In Figure 29, only 4 sub-machines are shown for each electric machine for convenience. Subsets or all of the electric sub-machines 1402’, 1404’, 1406’ and 1408’ has a motor controller 1412’, 1414’, 1416’ and 1418’. The motor controllers 1412’, 1414’, 1416’ and 1418’ are preferably mounted close to their respective electric sub-machines 1402’, 1404’, 1406’ and 1408’. The motor controllers 1412’, 1414’, 1416’ and 1418’ may be mounted in endcaps or housings of said electric sub-machines 1402’, 1404’, 1406’ and 1408’. A master motor controller 1420 may be provided to control the plurality of motor controllers 1412’, 1414’, 1416’ and 1418’, although this is not essential. A wiring loom 1411 comprising cables or circuits carrying power from the one or more energy storing units 1410 to the motor controllers 1412’, 1414’, 1416’ and 1418’ and the electric sub-machines 1402’, 1404’, 1406’ and 1408’. The wiring loom 1421 comprises respective cable circuits 1422, 1424, 1426, 1428 for the electric sub-machines 1402’, 1404’, 1406’ and 1408’.

Taking again the example of a system running a continuous current of 1000A at a voltage of 48V to provide a power output would be 48,000W, it will be seen that, where the vehicle 1400 is provided with one multi-motor electric machine 1402 in accordance with the invention, said electric machine 1402 having 10 electric sub-machines 1402’ then each of the motor controllers 1412’ for the 10 electric sub-machines 1402’ will carry 100A and each of the cables or circuits 1422 will carry 100A which is a very significant reduction compared to the system using a conventional motor running 1000A. Again, although different in scale, Figure 28 indicates a copper saving of 88%.

Where the vehicle 1400 of Figure 28 is provided with four multi-motor electric machines 1402, 1404, 1406 and 1408 in accordance with the invention, each of said electric machines 1402, 1404, 1406 and 1408 having 10 electric sub-machines 1402’, 1404’, 1406’ and 1408’ then each of the motor controllers 1412’, 1414’, 1416’ and 1418’ for the resultant 40 electric sub-machines 1402’, 1404’, 1406’ will carry 25A and each of the cable circuits 1422 will carry 25A which is a still more significant reduction compared to the system using a conventional motor running 1000A. It will be understood that compared to the 1000A vehicle system which requires specialized electrical cables, connectors, motor controller components, etc., the system having, for example, 4 electric machines 1402, 1404, 1406 and 1408 each with 10 electric sub-machines 1402’, 1404’, 1406’ and 1408’ can use “off the shelf’ electrical cables and connectors and low cost motor controllers.

Figure 30 shows an electric vehicle 1500 with a similar vehicle configuration to that of Figure 28, but where there is a plurality of energy storing units 1510A, 1510B, 1510C and 1510D, each of said energy storing units 1510A, 1510B, 1510C and 1510D being connected to different subsets of said electric sub-machines 1502’, 1504’, 1506’ and 1508’. In this vehicle configuration, an advantage is that smaller, more easily replaceable energy storing units 1510A, 1510B, 15 IOC and 1510D can be used compared to the typical single large integrated battery storage system found on most electric vehicles. The plurality of energy storage units 1510A, 1510B, 15 IOC and 1510D can be distributed around the vehicle for ease of access as well as to better balance the vehicle. The plurality of energy storing units 1510A, 1510B, 15 IOC and 1510D can be interconnected so that they can be charged via a single charging point 1560, although separate charging points for said energy storing units 1510A, 1510B, 15 IOC and 1510D may be provided in some vehicle configurations.

Figure 31 shows a stripped-down multi-motor electric machine 100 in accordance with the invention and which may be utilized in a vehicle 1300, 1400, 1500. The output gears 106 of said electric sub-machines 102 are visible, but the primary output gear 150 is not shown. At opposing ends of the electric sub-machines 102 to the output gears 106 are provided the motor controllers 1412’, 1414’, 1416’ and 1418’ and their respective cable circuits 1422, 1424, 1426, 1428. An end plate 1460 may be provided to mount heat dissipating devices such as heatsinks 1462.

As shown in Figure 32, in a vehicle having one multi-motor electric machine 100 according to the invention, the electric machine 100 may be connected to a vehicle axel unit 1560 through a gearbox 1562 of the vehicle 1300, 1400, 1500. Figure 33 shows the same arrangement of the electric machine 100 with the axel unit 1560 but with the electric machine 100 connected to the axel unit 1560 in an opposing orientation.

The electric machine 100 according to the invention can be configured with an array of motor controllers with each motor controller configured to control a subset of one or more of the plurality of electric sub-machines 102. This enables each motor controller to be connected to its subset of the plurality of electric sub-machines by cables sized in relation to a maximum power amount required by said subset of the plurality of electric sub-machines during operation as illustrated by Figure 28. Similarly, the cables connecting the electrical energy storage device to a motor controller can be sized in relation to a maximum power amount required by said motor controller’s subset of the plurality of electric sub-machines during operation. The same principle can apply to conductive paths on one or more circuit boards of a motor controller which can also be sized relation to a maximum power amount required by said motor controller’s subset of the plurality of electric sub-machines during operation. It is preferred that any of the cables or circuits connecting the motor controller to its subset of electric sub-machines, cables connecting the electrical energy storage device to the motor controller, or conductive paths on one or more circuit boards of the motor controller are low voltage cables or conductive paths.

A significant technical advantage of the electric machine described herein is that, even if one or more of the electric sub-motors fail, the electric machine can continue to operate albeit at a lower maximum output torque or power.

While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only exemplary embodiments have been shown and described and do not limit the scope of the invention in any manner. It can be appreciated that any of the features described herein may be used with any embodiment. The illustrative embodiments are not exclusive of each other or of other embodiments not recited herein. Accordingly, the invention also provides embodiments that comprise combinations of one or more of the illustrative embodiments described above. Modifications and variations of the invention as herein set forth can be made without departing from the spirit and scope thereof, and, therefore, only such limitations should be imposed as are indicated by the appended claims.

In the claims hereof, any element expressed as a means for performing a specified function is intended to encompass any way of performing that function including, for example, a) a combination of circuit elements that performs that function or b) software in any form, including, therefore, firmware, microcode or the like, combined with appropriate circuitry for executing that software to perform the function. The invention as defined by such claims resides in the fact that the functionalities provided by the various recited means are combined and brought together in the manner which the claims call for. It is thus regarded that any means that can provide those functionalities are equivalent to those shown herein.

In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art.