Construction and mode of operation of opposite statorless electronically switched motors

The invention relates to the construction and a mode of operation of statorless electronically switched DC motors that have two freely turning rotors. The invention also relates to embodiments of the invention regarding the bearings, the circuit design and the mode of operation of machines such as fans and blowers.

This invention relates to brushless direct current motors without commutating brushes and without stator. These motors are electronically switched motors and consist of two rotors which are freely movable in opposite direction, whereby these rotors are generally configured as inner or as outer rotor so that the magnetic field acts through a cylindrical air gap. Such a motor is known from the international application PCT-RO 00012/95.

The invention can also be applied to motors with plane axial air gap. One of the rotors, called hereunder “field rotor1”, is active, whereby it conducts current, the effect of the current conduction creating a rotating magnetic field due to field coils. The other rotor, called hereunder “secondary rotor2”, is passive and consists of a bundle of laminations, as usual for reluctance motors (SR motors). For other motor construction types, this rotor can also be configured as a motor with permanent magnets.

Each electronically switched motor can be transformed into a motor according to the invention, when the present stator can rotate freely by means of additional bearings31,32and thus becomes a field rotor. The opposite rotors are accordingly fixed on a carrier with bearings and are supplied with plus or minus current over two rotating contacts over two brushes.

The switching electronics of the motor13belongs to the field rotor and rotates accordingly together with it.

The control electronics143can be mounted either on the frame14of the field rotor1(FIG. 5b), or outside thereof, whereby it cooperates with the switching electronics15by electroplating contact (additional brushes) or by magnetic or optical coupling. These motors supply the useful effect over two opposite rotors which are loaded with the same torque, whereby their number of revolutions can be different. Therefore, it is necessary that the invention also offers the skilled in the art the solutions for the application of this unusual motor type. This is the condition for the realization of technically and economically competitive working units.

The aim of this invention is thus to offer experts in the field of electronically switched motors or experts in the field of working devices (especially ventilators) alternatives for solutions of embodiments so that they can realize optimized working units.

This is also necessary to allow an appropriate cooperation of experts of different specialities because without an understanding of the whole device each person skilled in the art could tend to apply traditional solutions which do not lead to optimal results.

The aim of this invention is achieved in claim 1 and is concretized in further individual alternatives which correspond to the subclaims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The parts which are driven by the rotor1and which rotate with it in one direction are represented in the drawings by left inclined hatching and have reference numerals which begin with the number 1 and those which rotate with the rotor2in opposite direction are represented by right inclined hatching and by numbers beginning with 2. The non rotating parts are represented by vertical hatching, eventually by crossed haching and have reference numerrals which begin with 3.

Should no hatching exist, the beginning number of the reference numeral shows the type of motion. The power connections (brushes) are indicated with (+) or (−) and the control parts are represented by a logic stage (high/flow).

FIGS. 1a, b, crepresent three construction alternatives of an opposite motor which are respectively derived from the concepts of former motors with an inner rotor (a), an outer rotor (b) of a former motor with an axial air gap (c). The reference numerals of all three drawings designate parts with the same function according to the above mentioned rules, as follows.1represents the field rotor (with windings).11is a hollow shaft through which the power connections or the control lines are guided and which is connected with the field rotor.12is a contactless sensor (magnetic or optical).13are power semiconductors which control the rotating field of the field rotor.14is a flange to which the driven device is mechanically coupled which belongs to the multifunctional motor frame.15is a line which represents the path of the power lines or control lines (through the hollow shaft11or the field rotor1).16is a Hall sensor which determine the rotor position,2represents the following rotor (with or without magnets)22is the bearing which belongs to this rotor which serves here as a bearing with respect to the hollow shaft11.24is the flange for coupling the driven aggregate.25is a magnetic disk for determining the rotor position.31,32represent the fixed bearings.33is the plus brush.34is the minus brush.35is a brush for the control (if necessary).36is a emitter which acts on the sensor12.37is the simplified representation of a frame closed against the environment which is sealed over one of the bearings31,32so that, the brushes are separated from the environment.

FIG. 1arepresents a motor for which the carrier bearings31,32are fixed on both sides of the rotors. According toFIGS. 1b, cthe carrier bearings31,32are fixed only on one side. The three motors ofFIGS. 1a, b, ccan naturally be realized with one of the three alternatives for the arrangement of the bearings31,32of the brushes33,34,35or of the sensors12or of the control emitter36.

FIG. 2shows more details of the basic construction of a motor with the following rotor as an inner rotor (FIG. 1a), for example as, for a motor which is known from the application PCI-RO 00012/95. The following rotor2which freely rotates with respect to the hollow shaft11, is fixed on an intermediate plate which extends between the first one and the bearing bush22and which ends with a flange24, what serves for the coupling of the driven object. The rotor2also carries a magnetic disk25which serves as a transmitter for the relative position of the rotors1and2, the field rotor1carrying correspondingly a Hall sensor16. The field rotor1is fixed on the hollow shaft11by means of a multifunctional frame14which carries the yokes141with the windings142. The driven device is fixed to the outer edge of the frame14. The windings142are connected with the printed board143, where the connections of the power transistors13are also fixed, whereby these transistors use the frame14as a cooler, the current flows from the pulse connection of the source of current through the brush33which contacts the axial pin111which is insulated with respect to the shaft. The pin111is drilled and protected so that it acts as a nut part of a plug-in connection (for exampleFIG. 3a). The radial plug pin145traverses it and is insulated against the frame14and thus conducts the current from the + connection to the printed board143. Other alternatives can also be realized, so for example the pin145can be first inserted, the pin111being then inserted into it. The minus connection of the source of current is connected with the brush34which pushes directly onto the shaft11which is directly in contact with the frame14so that the motor parts are on the minus potential.

With these simply realized connections, the motor is already operative. An abnormal increase of the number of revolutions of the motor, especially of the outer rotor, can be avoided by means of a contact which is fixed on the printed circuit143an which is actuated over the centrifugal force when a predetermined number of revolutions is exceeded. Should it be possible to influence the control of the electronics of the motor (printing board143) in order, for example, to start the motor or to control its power, this can be achieved by means of the sensor12. This sensor shows for example three connections111which are placed in an insulating body. The connections121of the sensor12which are placed around 120° on a circle are connected with the pins146which are insulated with respect to the frame14, these pins being connected with the printed board.

The insulating body122can be produced by injection moulding or by another processing from a thermoplastic or not thermoplastic material. In a simple form, this body can show grooves which receive the connections121. Here, known rules from the prior art are used in order to realize a safe electric connection between the lamellae121and the pins146. For example, it can be processed so that the pins146are inserted (radially) with, an elastic pressure into the lamellae121or that the lamellae121elastically engage (axially) into the pins146.

When this is desired, other connection techniques can also be used, for example by means of coaxial tubular lines which lead to slip rings or to the sensor12, whereby it is thus avoided that the hollow shaft11acts as a conductor. Insulated wires can also be drawn through the motor frame14and the hollow shaft11.

However, the embodiment example according toFIG. 2is simpler and is appropriate for an automatized assembly. A compact construction alternative for the brush arrangement which is appropriate for high currents is represented inFIG. 3bwhere two brushes33and33′ (or34,34′) are placed symmetrically opposite the pin111, their electric connections being switched in parallel and each brush being pressed by a double scroll spring33.

For the motor control, the emitter36transmits contactless control signals to the sensor12which acts onto the rotating electronics. The fixed bearings31and32allow that the shaft11freely rotates and take over supporting forces which are caused by the whole opposite arrangement. Both ends of the hollow shaft11are situated inside closed spaces37and37′, the sealing of the bearings31,32being used for the protection of the brushes and of the unit emitter/receiver, whereby the housings37,37′ are simultaneously supports of the motor.

Characteristic for these motors with opposite rotors is that they supply the same torque over each of the rotors1,2so that only a negligible friction moment is transmitted onto the support37, this moment coming from the brushes33,35or the bearings31,32.

The dimensioning number of revolutions for the electrics of the motor (the relative number of revolutions or the switching frequency) is the sum of the absolute numbers of revolutions of both rotors1,2all the more since they rotate in opposite direction. The number of revolutions and eventually the power of the motor can be controlled from outside even without the sensor12, by evaluation of the voltage and of the current on the brushes33,34of the motor as well as over the frequency of the current ripple which can be assigned to the commutation. These parameters can, if necessary, be adjusted by means of electronics which is placed outside the motor, for example in the stationary carrier.

The numbers of revolutions of both rotors1,2can be different and the number of revolutions of an individual rotor can be influenced (for example by changing the number of revolutions/the torque characteristic of the driven device), whereby the torque or the number of revolutions is also modified on the other rotor (2,1).

These are thus possibilities for controlling both working devices19,29which are driven by the rotors1and2, whereby the commutating frequency and or the ratio of the numbers of revolutions of the rotors can be influenced.

The preferred domain for the application of opposite motors of this invention is the actuation of axial opposite ventilators. The realization possibility of such a ventilator with several stages (four) is shown in FIG.4. The outer rotor1drives two axial ventilator stages b and d with blades18which rotate in a direction, the inner rotor2driving the stage a or the stage c over the foot of the ventilator blades29, the stage c being fixed to the stage a over a simultaneously rotating cylindrical tube27.

The wall (the carrier)38which separates the overpressure spaces (P) or the underpressure spaces (J) can be configured as an extension of the housings of the bearings31,32or of the brushes33,34. It shows a cylindrical collar in the area of the stage d (air inlet) in order to reduce the losses between the collar and the tube27.

For applications which require a high throughput for a low pressure, the alternative of an opposite motor with two ventilators according toFIGS. 5a, bis advantageous (schematic representation and motor cross section).

The motor according toFIG. 5b(driving gear arrangement, seeFIG. 5a) shows the configuration of two rotors as inFIG. 1a, the bearing arrangement corresponding toFIG. 1b. Here, the outer rotor1drives the blades19of a ventilator and the inner rotor2drives a laterally offset placed ventilator29by means of the belt241so that both ventilators work parallel the one besides the other. The transmission ratio of the belt drive241driven by the inner rotor2over the belt wheel (flange)24can be 1:1 or be different and, if necessary, can even be changed so that additional control possibilities could be achieved. The remaining parts are designated as in FIG.1. The ratio of the powers required by the two ventilators can be obtained by changing the ventilator characteristic by known methods.

If we consider that both torques are the same, the operating point of each ventilator can be determined. The two ventilators can be placed in the same plane (FIG. 5) or in different planes.

FIG. 6shows two radial blowers19,29, each one with a spiral blower, which are driven by the rotors1and2according to the invention. InFIG. 7, there is an alternative with two radially concentrical blowers19,29which are driven by the rotors1,2, the one blower wheel being placed inside the other. This type does not require any spiral housing, air being blown in radial direction. The invention allows the realization of economically easy and efficient motor/blower units by simple technological methods.