Blade-type electric motor-generator

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The invention concerns the field of electric motors. More specifically, the purpose of the invention is a new type of reversible electric motor, suitable for operating as well as a fluid machine and especially as a pump (or compressor) or driving machine.

In the prior art, electric motors and generators are used in a range of different fields and in all power classes. Some electric motors (for example the DC and permanent-magnet motors) are also known to be reversible, i.e. they can also operate as electric current generators.

A very common application of electric motors consists in driving machines like fans, pumps and compressors: an example is given by common motor-driven pumps. In the same field, reversible electric motors are also coupled to reversible fluid machines, like e.g. hydraulic turbines that can reverse their direction of rotation and also operate as pumps. Such a unit can operate both as a motor-pump and turbine-generator.

Another particular field of use of the invention is that of the electric traction of vehicles and cars. In recent years, electric-powered cars have become of extreme interest, and this is considered one of the most interesting solutions for future developments in the automotive industry. Electric motors do not produce exhaust fumes and local pollution, are silent and allow a considerable simplifying of the vehicle

(they do not require a clutch, a gearbox, etc.). An electric car is considered a zero-emissions vehicle, and can access town and city

centres that are closed to traffic, thereby overcoming a problem which is now affecting drivers to an increasing extent.

The direct-current permanent-magnet motor, in particular, has a number of characteristics that make it especially suitable for vehicle traction: it delivers high torque at low rotation speeds, useful for start and breakaway; it is compact, it can also operate as a brake and/or generator and thus permits to recover a certain amount of energy during deceleration.

In this field, however, there are limits substantially due to the weight and overall dimensions of the batteries, forcing to use motors of no more than a few dozen kW. This power shows to be insufficient on medium/large vehicles, and, generally speaking, leaves the need for an extra power for accelerating, overtaking and emergency manoeuvres. It should also be borne in mind that a modern car is burdened by a large number of accessories, including the air- conditioning system, which demand a lot of energy.

Currently such limit is overcome by hybrid vehicles, that is by vehicles provided with an internal combustion engine that can operate together with the electric motor, with the drawback, however, of a more complicated and expensive vehicle having actually two motors.

As regards, more specifically, aspects relating to the manufacture of direct-current motors with permanent-magnet rotor, the prior art document US 6.049.149 describes a brushless DC motor with a permanent-magnet rotor and a pair of wound-wire stators, arranged on opposite sides of the rotor, having Hall effect sensor control.

The adoption of two stators at the sides of the rotor permits to double the number of poles and to obtain greater torque and power, dimensions being equal. Nevertheless, the previously summarised drawbacks remain. The purpose of the invention is to overcome the known state of the art, and its limitations, by means of a newly-conceived motor- generator substantially suitable for: operating directly as a fluid operating machine (pump or compressor) without being coupled to an external machine; - operating in a reversible way, both as an electric motor and as a generator; providing, when used as a motor, greater power availability, compared to the rated electric power, useful for example in the traction industry. Further purposes of the invention are to make a motor that is easy to build, and with high power output in relation to its weight and size.

The purposes are achieved with an electric motor-generator comprising: an external armature; - a permanent-magnet rotor; a pair of wound-wire stators, arranged at opposite sides of the rotor and integral with the armature; a control system; wherein: - the rotor comprises a plurality of moving blades, directed

substantially in a radial direction from the rotor to the armature, and sliding in a radial direction with respect to said rotor;

- the armature features a plurality of respective supporting profiles for said moving blades, arranged to define an equal number of compression or expansion chambers, of variable volume, arranged in the space between the rotor and the armature;

- the armature has at least one pair of fluid inlet and outlet openings for each of said chambers.

Preferably, the rotor consists of a plurality of magnets, each extended over a determinate round sector; the blades are slide-fitted in the spaces between one magnet and another.

Again preferably, the blades are substantially made with a number of sliding magnets, separated from the actual rotor magnets by means of non-magnetic spacers, for example made of teflon or ceramic material.

The motor can be made with modular structure, with separated compression or expansion chambers, with dedicated inlets and outlets. This way the motor is able to also process different kinds of fluids. The motor - generator according to the invention achieves the above purposes. In particular, it offers the advantages described below.

A first advantage is that the motor can operate directly, i.e., without being connected to another machine, such as a pump or compressor of a gas or a liquid, as the rotor itself, thanks to the moving blades,

represents the impeller.

Another advantage consists in the possible use as a driving machine, with a liquid or gas fluid under pressure being supplied to the motor. This operating mode is also possible together with electric drive, to deliver a supplementary mechanical power, with respect to the rated power of "electric only" operation.

The motor is also fully reversible, and can also operate as an electric generator, thus receiving mechanical power from the shaft and producing electricity. The advantages are particularly useful, but not limited to, the automotive industry, for a purely electric or hybrid vehicle. Because it can operate as a pump or compressor, including with different fluids, the motor can replace a number of auxiliaries such as air-conditioning system compressor, oil pump, water pump, etc.... The capacity to use a fluid under pressure as motor fluid can be exploited to have additional power for short periods of time, for example for overtaking; furthermore, the motor can operate as a brake or act as a generator and recover energy when the vehicle is braking.

The invention is now described in greater detail with the help of the illustrations, in which:

Fig. 1 schematically represents a longitudinal section of a motor- generator according to the invention, and shows the main component parts;

Fig. 2 schematically shows a cross section, according to a plane perpendicular to the axis, of the motor of Fig. 1.

With reference to the figures, a motor-generator is shown according to the invention, which essentially comprises an armature 1, a permanent-magnet rotor 2 and two wound-wire stators 3 and 4, arranged on opposite sides of the rotor 2. The stators 3 and 4 have a suitable number of windings 5, which can be driven in direct current (DC) by a specific circuit, not shown. Control is entrusted to an electronic system which, preferably, is of the type described in patent No. IT-1304969 by one of the applicants.

The rotor 2 is associated with a motor shaft 6 running on bearings 7. The direction of rotation of the rotor 2 is unique and is indicated by the arrow R in Fig. 2. The position of the rotor 2 with respect to the armature 1 can be defined by the angular coordinate ω shown in Fig.

2.

The rotor 2 has a plurality of blades 8, which extend in a substantially radial direction from the rotor towards the armature 1 , and are movable in a radial direction.

There are a variable number of blades 8, depending on the project; in the example the rotor comprises four blades spaced at 90 degrees.

The armature 1 , on the inner part in ferromagnetic material, has respective supporting profiles 9 for the moving blades 8, facing the rotor 2.

Each supporting profile 9, as seen in Fig. 2, extends along an arc

A. The radial thickness of the profile 9 varies in a monotone way along said arc A, from an initial section in which the profile 9 practically lies on the armature 1 , to an end section where clearance between the

profile 9 and the rotor 2 is minimum.

The supporting profile 9, in other words, has a surface 10, facing the rotor 2, with a curved pattern, preferably a circular arc, delimiting a chamber 11 in the space between the rotor 2 and the armature 1. Said chamber 11 has a radial dimension or height h (Fig. 2), corresponding to the clearance between the rotor 2 and the facing surface 10, and said height h is variable with the angular coordinate ω between a maximum and a minimum value. Said height h, as can be seen, gradually drops along the arc A of extension of profile 9, following the direction of rotation R of the motor.

A portion 11a having a constant height, and a portion 11b where the height depends on the angular position ω decreasing in the direction of rotation R, can substantially be seen into the chamber 11.

The armature 1 has openings that communicate with the chamber 11 , for inlet/outlet of liquid or gaseous fluids like e.g. water, steam, oil or any other gas or liquid.

Each chamber 11 has at least a first opening 12 and a second opening 13. The first opening 12 communicates with the portion 11a with constant height; the second opening 13 communicates with portion 11b, and is preferably located near the end of said portion 11b, where the height h is minimum or close to minimum value.

An arc portion can also be provided at the end of the curved section of the portion 11 b, instead of the step which can be seen in Fig. 2, to better accompany the blade 8 at the end of the movement along the profile 9.

In the illustrated embodiment, the rotor 2 comprises four permanent magnets 14, which extend substantially over a sector of 90 degree each, and among which an equal number of moving blades 8 is fitted.

The moving blades 8 are also made with magnets, and are slide-fitted in channels 15 between one magnet and another. The blades 8 are separated from the magnets 14 by non-magnetic spacers 16.

The blades 8 are attracted by magnetic force against the armature

1 ; in one embodiment of the invention, thrust springs can also be fitted, inserted in the channels 15. The motor can also be made to compress or expand a plurality of different fluids at the same time, exploiting the fact that it comprises a plurality of chambers 11 separate from one another (four in the example shown) or the motor can be made in modular shape, by means of a plurality of units like the one of Fig. 1. Other construction details are not described, inasmuch as they belong to the state of the art or are in any case accessible to technicians in the field.

Operation is as follows: the unit can operate simply as an electric motor with permanent magnets, of the known type, or as a generator of electric current, in the event of the rotor 2 being driven by the shaft

6.

The unit is also able to operate as a fluid operating machine: in particular it can compress a gas or a liquid supplied through the openings 12. Looking at Fig. 2, in fact, it can be seen that the rotation of the rotor

2, with the blades 8 pushed in support on the surfaces 10 of the profiles 9, can compress the fluid contained in the chambers 11 , with an operating principle that is substantially similar to that of a positive- displacement blower pump. The volume of fluid, moving along the angular coordinate ω, is compressed inside the portion 11b of the chamber, by effect of the gradual reduction of height h. The compressed fluid is then discharged from the openings 13, as shown by the arrows.

Due to a complete rotation of the rotor 2, the same compression effect is obtained which is repeated in the various chambers 11 (four in the example embodiment shown). The arrows in Fig. 2 indicate fluid inlet and outlet.

Vice versa, the introduction of a fluid under pressure in the chambers 11 , by causing a thrust on the blades 8, can start the rotation of the rotor 2, with an operation similar to a positive- displacement motor.

A preferred application consists in driving electric or hybrid vehicles, in which the motor according to the invention can be housed in the motor compartment or even coupled directly to the wheels. Thanks to its capacity to also operate as a pump or a compressor, the motor can perform the functions of a number of auxiliaries such as air-conditioning system compressor, water pump, etc...