WO2013167096A2

WO2013167096A2 - Compact driving unit

Info

Publication number: WO2013167096A2
Application number: PCT/CZ2013/000061
Authority: WO
Inventors: Filip PLESINGER; Miroslav BEHAVKA
Original assignee: Evektor, Spol. S.R.O.
Priority date: 2012-05-11
Filing date: 2013-05-09
Publication date: 2013-11-14
Also published as: CZ303973B6; CZ2012312A3; WO2013167096A3

Abstract

The compact driving unit comprises an array of switched two-pole reluctance electric motors (1), the rotors (2) of the latter being mutually coupled for propelling the output gear of the driving unit and shifted relative to the respective stators (2) in regular angular spacings in order to compensate for the torque variations of the driving unit, and a processor for controlling the individual switched reluctance electric motors (1).

Description

Compact Driving Unit Technical field

The invention relates to a compact unit comprising an array of switched reluctance electric motors.

State of the art

Vehicles or machines of any kind can be driven by an electric motor that is powered by electricity drawn either from an electric accumulating device or directly, i.e. immediately, from a power distribution network. In the case of autonomous vehicles or machines, which are powered by accumulated

electricity, the components used must meet exacting requirements relating to low weight and compact design.

In order to enable the practical application comprising an electric motor to be implemented, the highest possible performance parameters per unit weight along with the highest possible range per accumulation cycle of the storage devices installed within the vehicle, such as batteries, capacitors, accumulating units, fuel cells or the like, should be achieved.

The most important prerequisite for the making use the most of the available accommodating space within the vehicle consists in minimizing the dimensional parameters of the components of the electric driving unit used. Due to the need of achieving the maximum possible performance parameters of the driving unit of a vehicle or machine per unit weight, it is necessary to reduce the weight of the components of the driving unit used up to a minimum level.

However, such reduction must not adversely affect the sufficient sturdiness of the components. These aspects, in turn, influence the reliability and durability of the driving unit. At same time, the latter must also exhibit a high degree of safety in order to meet the corresponding requirements of the applicable laws and standards. The accommodating space of an electric driving unit is often considerably limited by the spatial arrangement of the individual subassemblies of the respective vehicle or machine which are dedicated for the primary intended use of the latter.

For the above reasons, the capacity of the devices used in vehicle or machines for accumulating electric power is limited which leads to the reduction of the respective range per charge.

In the case of autonomous vehicles or machines, which are equipped with electric motors powered by accumulator cells, the spatial as well as weight requirements placed by the contemporary accumulators are very demanding. Therefore, it is necessary to design the respective vehicle or machine in a manner that will allow a sufficient accommodating space for the accumulator cells to be reserved. The main decisive factors are the applicable weight limitation of the individual vehicle categories along with the respective range per charge. In addition, the arrangement of other subassemblies of a vehicle or machine have to be considered. The ongoing minimization of the individual components, regarding both their weight and their dimensions, enables accumulators having higher capacities to be used. This favourably influences the range per charge or the autonomous operation of a vehicle or machine.

Summary of the invention

The above mentioned drawbacks of the prior art are largely eliminated by the compact driving unit according to the invention, wherein the compact driving unit comprises an array of switched two-pole reluctance electric motors, the rotors of the latter being mutually coupled for propelling the output gear of the driving unit and shifted relative to the respective stators in regular angular spacings in order to compensate for the torque variations of the driving unit, and a processor for controlling the individual switched reluctance electric motors. Possible irregularities in the geometric arrangement of driving unit comprising an array of switched two-pole reluctance electric motors can be corrected with the use of the parameters included in the control program of the processor.

In a preferred embodiment of the invention, the rotational axes of the rotors are parallel to each other.

In a further preferred embodiment of the invention, the output gear of the driving unit comprises a driven shaft of the driven shaft for transmitting the torque developed by the switched two-pole reluctance electric motors.

In another preferred embodiment of the invention, the output gear of the compact driving unit comprises either a toothed gearing and/or a chain drive and/or a toothed-belt drive for transmitting the torque developed by the switched two-pole reluctance electric motors.

In yet another preferred embodiment of the invention, the driven shaft of the driving unit is coupled with the driving shaft of an electric vehicle in order to transmit the power to the driven wheels of the electric vehicle.

In a particularly preferred embodiment of the invention, the compact driving unit comprises n switched two-pole reluctance electric motors having their rotors or stators mutually shifted in angular spacings of 180 n, wherein n is a natural number ranging between 2 and 8. Thus, the compact driving unit may comprise, e.g., three switched two-pole reluctance electric motors having their rotors or stators mutually shifted in angular spacings of 60° or four switched two-pole reluctance electric motors having their rotors or stators mutually shifted in angular spacings of 45°.

In a particular advantageous embodiment, the stators of the switched two- pole reluctance electric motors are made of metal sheets having more than 2 mm, preferably 4 mm, in thickness. In a more advantageous embodiment, the stators of the switched two-pole reluctance electric motors are made of a single piece of a magnetic material. In another preferred embodiment of the invention, at least two rotors share one common shaft.

In another preferred embodiment of the invention, the switched two-pole reluctance electric motors are arranged side by side and their rotors are provided with toothed wheels, the neighbouring wheels being in mutual engagement.

The above mentioned drawbacks of the prior art are also largely

eliminated by an electric power generator comprising a set consisting of the above described compact driving unit. Brief description of the drawings

For more detail, the invention will be further described with reference to the accompanying drawings where Fig. 1 schematically illustrates the first exemplary embodiment of the compact driving unit without showing the switched two-pole reluctance electric motors that are mutually coupled, Fig. 2 schematically illustrates the second exemplary embodiment of the compact driving unit, also without showing the switched two-pole reluctance electric motors that are mutually coupled, Fig. 3 schematically illustrates a further exemplary embodiment of the compact driving unit along with the arrangement of the mutually coupled motors, Fig. 4 illustrates an alternative of the

embodiment shown in Fig. 3, incorporating a central gear wheel with internal teeth, Fig. 5 schematically illustrates another exemplary embodiment of the compact driving unit used for propelling an airscrew, Fig. 6 schematically illustrates a further exemplary embodiment of the compact driving unit, where all the stators have a common stator-core lamination, and Fig. 7 schematically illustrates a cross section of the driving unit according to the invention.

Exemplifying embodiments of the invention

Fig. 1 schematically illustrates the first exemplary embodiment of the compact driving unit according to the invention. The compact driving unit comprises the array of three switched two-pole reluctance electric motors 1 having their rotors 2 mutually coupled (in a manner that is not shown) for propelling the output gear of the driving unit. The output gear of the compact driving unit may comprise the driven shaft 6 of the same, simultaneously serving either as driving shaft for a gearbox or for a final drive of a vehicle or as driving shaft for a driven travel wheel of a vehicle. In other embodiments, the output gear of the compact driving unit may be formed either directly by the driven road wheel of a vehicle or a central hub of an airscrew 9 or marine propeller. The airscrew 9 may either serve for propelling an aircraft or constitute a component of a wind power station. In the latter case, the array of three switched two-pole reluctance electric motors will assume the function of an electric power generator. The marine propeller may either serve for propelling a watercraft or constitute a component of a hydro-electric power station. In the latter case, the array of three switched two-pole reluctance electric motors will assume the function of an electric power generator. The stators 4, which are parallel to each other, are provided with phase windings 5. The rotors 2 are positioned in regular angular spacings of 60° with respect to the respective stators in order to compensate for the torque variations of the driving unit.

Possible irregularities in the geometric arrangement of driving unit comprising an array of switched two-pole reluctance electric motors 1 may be corrected with the use of the parameters included in the control program of a control processor (not shown).

Fig. 2 schematically illustrates the second exemplary embodiment of the compact driving unit according to the invention, being different f om the first exemplary embodiment in that the rotors 2 are arranged in parallel to each other and the respective stators 2 are positioned in regular angular spacings of 60° with respect to the rotors in order to compensate for the torque variations of the driving unit. Fig. 3 schematically illustrates a further exemplary embodiment of the compact driving unit along with the arrangement of the mutually coupled motors. The driving unit is provided with an output gear comprising the driven shaft 6 for transmitting the torque developed by the switched two-pole reluctance electric motors 1. Each rotor 2 is provided with the gear wheel 7 that is in permanent engagement with the central gear wheel 8 with external toothing, the latter wheel being rigidly fixed to the driven shaft 6 of the driving unit. The combination of the gear wheels 7 and the central gear wheel 8 with external teeth constitute a gearing mechanism through which the torque developed by the individual switched two-pole reluctance electric motors 1 is transmitted to the driven shaft 6 of the driving unit.

Fig. 4 schematically illustrates a further exemplary embodiment of the compact driving unit along with the arrangement of the mutually coupled motors. In contrast to the preceding embodiment, the gear wheels 7 are in permanent engagement with the central gear wheel 8 with internal toothing, the latter wheel being rigidly fixed to the driven shaft 6 of the driving unit. The combination of the gear wheels 7 and the central gear wheel 8 with internal teeth constitute a gearing mechanism through which the torque developed by the individual switched two-pole reluctance electric motors 1 is transmitted to the driven shaft 6 of the driving unit.

Fig. 5 schematically illustrates another exemplary embodiment of the compact driving unit where torque is transmitted to a driven unit directly. This means that no intermediate driven shaft 6 of the driving unit is used. In this manner, a direct propulsion of a road, wheel airscrew or marine propeller can be achieved. In the exemplary embodiment shown in Fig. 5, the central gear wheel 8 is directly and rigidly fixed to the driven unit constituted by the airscrew 9.

Fig. 6 schematically illustrates a further exemplary embodiment of the compact driving unit consisting of three switched two-pole reluctance electric motors 1, the rotors 2 being mutually coupled by means of a gearing mechanism consisting of the toothed wheels 7 of the rotors 2, the teeth of said wheels being in permanent engagement with the toothing of the central gear wheel 8 that is rigidly fixed to the driven shaft 6 of the driving unit. In this embodiment, all three stators 4 share a common stator-core lamination.

Fig. 7 schematically illustrates yet another exemplary embodiment of the compact driving unit according to the invention in a cross-sectional view. As shown in the figure, the rotors 2 of the driving unit are mutually shifted with regular angular spacings of 45 °C. Possible irregularities in the geometric arrangement of driving unit comprising an array of switched two-pole reluctance electric motors 1 may be corrected with the use of the parameters included in the control program of a control processor (not shown).

In order to make the exemplary embodiments of the compact driving unit comprising an array of switched two-pole reluctance electric motors 1

operational, it is necessary to set up a control chain for that array. Such control chain comprises a system of sensors, such as rotary encoders for the rotors 2, voltage sensors, current sensors, temperature sensors and the like. The control chain is connected to a control unit comprising a processor, in which a control program is installed, and low-current electronic circuits. Furthermore, the control chain comprises the power electronic circuits which are connected to the phase windings 5 of the stators 4.

When the compact driving unit is in operation, a single rotary encoder (not shown) associated with one of the rotors 2 of the compact driving unit can define the instantaneous angular positions of the mutually coupled rotors 2 with respect to the corresponding stators 4. On the basis of the information received from the above rotary encoder, the control program of the processor takes the decision to send the corresponding control signals to the low-current electronic circuits in order to initiate the connection of the phase windings 5 of those stators 4 which, at the given moment, exhibit a favourable angular shift with respect to the pole pieces 10 of the two-pole reluctance electric motors 1, to the terminals of a power supply. The low-current electronic circuits process the above signal in a manner that enables the power supply to be connected to the phase windings 5 of the respective two-pole reluctance electric motors 1 through the power electronic circuits. When the electric current flows through the phase winding 5 of the stator 4 of one or more of the two-pole reluctance electric motors 1 having their rotors 2 suitably shifted with respect to the pole pieces 10 of the stators 4, the action of the developed electromagnetic forces causes the poles of the rotors 2 to be attracted to the pole pieces 10 of the stators 4, thus making the rotors 2 rotate. This happens until the control program, after having considered the information received from the rotary encoder associated with the rotors 2 and another information relating to the actual condition of the electrical quantities within the compact driving units, evaluates the necessity of stopping the current flow passing through the respective phase winding(s) 5 of the stator(s) 4. The current flow passing through the phase winding(s) 5 of the stator(s) 4 must cease to exist at latest at the moment when the poles of the rotor 2 are passing by those of the stator 4. If the current flow passing through the phase windings 5 of the stators 4 did not faded out within the given period of time, the forces acting on the rotors 2 would be reversed and the motion of the reluctance motors would decelerate or stop.

Thus, the supply voltage is connected to the individual phase windings of the stators 4 in a sequential manner so that the partial rotational travel of each rotor 2 covers the corresponding angular distance to the next pole piece 10 of the respective stator 4. After a rotor 2 has reached the position, in which it is adjoining the pole piece 10 of the respective stator 4, no torque is being generated in that rotor 2. However, since the rotors of the individual switched two-pole reluctance electric motors 1 are mutually shifted with regular angular spacings, such with spacings of 45°, the torque variations of the driving unit are equalized in that the required torque is always developed by the next rotor 2 which is suitably shifted with respect to the nearest pole piece of the corresponding stator 4. Since all the rotors 2 of one compact driving unit are mutually coupled, the rotor 2, which was previously adjoining the pole piece 10 of the respective stator 4, will gradually assume a position that will enable the torque in the desired direction of rotation to be developed. Thus, the output gear begins to rotate and its rotation is maintained by the alternating, and partly simultaneous, action of the individual switched two-pole reluctance electric motors 1. At any moment when one of the switched two-pole reluctance electric motors 1 is assuming a position, in which no torque is being developed in its rotor 2, a sufficient torque is being developed in at least one of the remaining switched two-pole reluctance electric motors 1 of the driving unit. In this way, the torque ripple of the output gear of the driving unit is largely eliminated and such driving unit exhibits substantially continuous speed and output.

The above described arrangements of multiple switched two-pole reluctance electric motors 1, which typically have the centrelines parallel to the rotational axis of a driven axle, enables the maximum utilization of the torque along with the minimization of the accommodating space needed for the driving unit to be achieved. At the same time, the arrangement of the switched two-pole reluctance electric motors 1 provides a high degree of spatial variability, as shown in the illustrations of the preferred embodiments of the invention. The switched two-pole reluctance electric motors 1 are characterized by a simple design, minimum manufacturing cost and maximum efficiency in developing the required torque. In addition, if such motors are suitably mechanically coupled, it is possible to obtain an almost equalized torque flow at the endpoints of the respective electric powertrain, such endpoints being e.g. the road wheels of a vehicle.

The above configurations of the electric driving unit can be used not only in place of an automobile engine, whose torque is transmitted to the individual axles or to the individual road wheels by means of a differential gear, but also for the direct propulsion of the individual road wheels. Each half axle of a motor vehicle can be fitted by its own compact driving unit, which enables the torque of the individual half-axle shafts to be electronically controlled. Thus, the overall driving performance of the vehicle can be optimized. The gearing provided with internal teeth can be also advantageously used to transmit the power developed by the array of switched two-pole reluctance electric motors directly to the individual road wheels of a vehicle, i.e. without any intermediate members.

Another advantage of the arrangements described with reference to the present invention consists in the reduced noise level when compared with other types of electric motors. This is due to the use of smaller, simple reluctance electric motors which are subject to intermittent loads. In this manner, the noise originating from the structural deformations of the electric motors is replaced by the mechanical noise produced by the gears, the elimination of the latter being easier.

Reluctance motors are capable to work in the generator mode, as well. This means that all the above mentioned preferred embodiments can be also utilized for electricity generation.

Industrial applicability

The compact driving unit according to the invention can be used in electric vehicles or other machines, particularly in those where internal combustion engines are undesirable due to the production of harmful emissions or due to the operation in an explosive environment. Furthermore, it can be used in hybrid vehicle powertrains.

Claims

Patent claims

1. Compact driving unit, characterized in that it comprises an array of switched two-pole reluctance electric motors (1), the rotors (2) of the latter being mutually coupled for propelling the output gear of the driving unit and shifted relative to the respective stators (2) in regular angular spacings in order to compensate for the torque variations of the driving unit, and a processor for controlling the individual switched reluctance electric motors (1).

2. Compact driving unit according to claim 1, characterized in that the rotational axes of the rotors are parallel to each other.

3. Compact driving unit according to claim 1, characterized in that the output gear of the driving unit comprises a driven shaft (6) of the driving unit for transmitting the torque developed by the switched two-pole reluctance electric motors (1).

4. Compact driving unit according to claim 1, characterized in that the output gear of the driving unit comprises a toothed gearing for transmitting the torque developed by the switched two-pole reluctance electric motors (1).

5. Compact driving unit according to claim 1, characterized in that the output gear of the driving unit comprises a chain drive and/or a toothed-belt drive for transmitting the torque developed by the switched two-pole reluctance electric motors (1).

6. Compact driving unit according to claim 1, characterized in that the driven shaft (6) of the driving unit is coupled with the driving shaft of an electric or hybrid vehicle in order to transmit the power to the driven wheels of that vehicle.

7. Compact driving unit according to claim 1, characterized in that it comprises n switched two-pole reluctance electric motors (1) having their rotors (2) or stators (4) mutually shifted in angular spacings of 180 n, wherein n is a natural number ranging between 2 and 8.

8. Compact driving unit according to claim 1, characterized in that the stators (4) of the switched two-pole reluctance electric motors (1) are made of metal sheets having more than 2 mm, preferably 4 mm, in thickness.

9. Compact driving unit according to claim 1, characterized in that the stators (4) of the switched two-pole reluctance electric motors (1) are made of a single piece of a magnetic material.

10. Compact driving unit according to claim 3, characterized in that at least two rotors (2) share one common shaft (6).

11. Compact driving unit according to claim 4 or 5, characterized in that the switched two-pole reluctance electric motors (1) are arranged side by side and their rotors (2) are provided with toothed wheels (7), the neighbouring wheels being in mutual engagement.

12. Electric power generator, characterized in that it comprises a set consisting of the compact driving unit according to claims 1 to 11.