Abstract:
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.

Description:
This application is a continuation of PCT/RO00/00009 filed Apr. 21, 2000. 
    
    
     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 rotor  1 ”, 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 rotor  2 ”, 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 bearings  31 ,  32  and 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 motor  13  belongs to the field rotor and rotates accordingly together with it. 
     The control electronics  143  can be mounted either on the frame  14  of the field rotor  1  ( FIG. 5   b ), or outside thereof, whereby it cooperates with the switching electronics  15  by 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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings illustrate the invention. In such drawings: 
         FIG. 1   a : Shows a construction alternative of the opposite motor with an inner rotor arrangement and with carrier bearings  31 ,  32  fixed on both sides of the rotors. 
         FIG. 1   b : Shows a construction alternative of the opposite motor with an inner rotor arrangement and with carrier bearings  31 ,  32  fixed only on one side. 
         FIG. 1   c : Shows a contruction alternative of the opposite motor with rotors separated by an axial air gap and with carrier bearings  31 ,  32  fixed only on one side. 
       FIG.  2 : Shows a more detailed configuration of the basic construction of the opposite motor. 
         FIG. 3   a : Shows axial pin  111  drilled so that it acts as the nut part of the connection with the radial plug pin  145  of FIG.  2 . 
         FIG. 3   b : Shows a brush configuration where two brushes  33 ,  33 ′ are placed symmetrically opposite the pin  111 , with each brush being pressed by a double scroll spring  331 . 
       FIG.  4 : Shows a four stage a, b, c, d ventilator operated by the opposite motor, a and c being operated by the inner rotor  2  by means of a cylindrical tube  27 , and b and d being operated by the outer rotor  1 . 
         FIG. 5   a : Shows the opposite motor with rotor arrangement according to  FIG. 1   a  and with bearing arrangement according to  FIG. 1   b.    
         FIG. 5   b : Shows the configuration of the opposite motor operating two ventllators  19 ,  29  In parallel by means of rotors  1 ,  2  and a belt  241 . 
       FIG.  6 : Shows the configuration of the opposite motor operating two radial blowers  19  and  29 , each one with a spiral housing. 
       FIG.  7 : Shows a radially concentrical blower unit with one blower wheel  19  being placed inside the other  29 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The parts which are driven by the rotor  1  and 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 rotor  2  in 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. 1   a, b, c  represent 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.
           1  represents the field rotor (with windings).     11  is a hollow shaft through which the power connections or the control lines are guided and which is connected with the field rotor.     12  is a contactless sensor (magnetic or optical).     13  are power semiconductors which control the rotating field of the field rotor.     14  is a flange to which the driven device is mechanically coupled which belongs to the multifunctional motor frame.     15  is a line which represents the path of the power lines or control lines (through the hollow shaft  11  or the field rotor  1 ).     16  is a Hall sensor which determine the rotor position,     2  represents the following rotor (with or without magnets)     22  is the bearing which belongs to this rotor which serves here as a bearing with respect to the hollow shaft  11 .     24  is the flange for coupling the driven aggregate.     25  is a magnetic disk for determining the rotor position.     31 ,  32  represent the fixed bearings.     33  is the plus brush.     34  is the minus brush.     35  is a brush for the control (if necessary).     36  is a emitter which acts on the sensor  12 .     37  is the simplified representation of a frame closed against the environment which is sealed over one of the bearings  31 ,  32  so that, the brushes are separated from the environment.       
       FIG. 1   a  represents a motor for which the carrier bearings  31 ,  32  are fixed on both sides of the rotors. According to  FIGS. 1   b, c  the carrier bearings  31 ,  32  are fixed only on one side. The three motors of  FIGS. 1   a, b, c  can naturally be realized with one of the three alternatives for the arrangement of the bearings  31 ,  32  of the brushes  33 ,  34 ,  35  or of the sensors  12  or of the control emitter  36 . 
       FIG. 2  shows more details of the basic construction of a motor with the following rotor as an inner rotor ( FIG. 1   a ), for example as, for a motor which is known from the application PCI-RO 00012/95. The following rotor  2  which freely rotates with respect to the hollow shaft  11 , is fixed on an intermediate plate which extends between the first one and the bearing bush  22  and which ends with a flange  24 , what serves for the coupling of the driven object. The rotor  2  also carries a magnetic disk  25  which serves as a transmitter for the relative position of the rotors  1  and  2 , the field rotor  1  carrying correspondingly a Hall sensor  16 . The field rotor  1  is fixed on the hollow shaft  11  by means of a multifunctional frame  14  which carries the yokes  141  with the windings  142 . The driven device is fixed to the outer edge of the frame  14 . The windings  142  are connected with the printed board  143 , where the connections of the power transistors  13  are also fixed, whereby these transistors use the frame  14  as a cooler, the current flows from the pulse connection of the source of current through the brush  33  which contacts the axial pin  111  which is insulated with respect to the shaft. The pin  111  is drilled and protected so that it acts as a nut part of a plug-in connection (for example  FIG. 3   a ). The radial plug pin  145  traverses it and is insulated against the frame  14  and thus conducts the current from the + connection to the printed board  143 . Other alternatives can also be realized, so for example the pin  145  can be first inserted, the pin  111  being then inserted into it. The minus connection of the source of current is connected with the brush  34  which pushes directly onto the shaft  11  which is directly in contact with the frame  14  so 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 circuit  143  an 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 board  143 ) in order, for example, to start the motor or to control its power, this can be achieved by means of the sensor  12 . This sensor shows for example three connections  111  which are placed in an insulating body. The connections  121  of the sensor  12  which are placed around 120° on a circle are connected with the pins  146  which are insulated with respect to the frame  14 , these pins being connected with the printed board. 
     The insulating body  122  can 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 connections  121 . Here, known rules from the prior art are used in order to realize a safe electric connection between the lamellae  121  and the pins  146 . For example, it can be processed so that the pins  146  are inserted (radially) with, an elastic pressure into the lamellae  121  or that the lamellae  121  elastically engage (axially) into the pins  146 . 
     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 sensor  12 , whereby it is thus avoided that the hollow shaft  11  acts as a conductor. Insulated wires can also be drawn through the motor frame  14  and the hollow shaft  11 . 
     However, the embodiment example according to  FIG. 2  is simpler and is appropriate for an automatized assembly. A compact construction alternative for the brush arrangement which is appropriate for high currents is represented in  FIG. 3   b  where two brushes  33  and  33 ′ (or  34 ,  34 ′) are placed symmetrically opposite the pin  111 , their electric connections being switched in parallel and each brush being pressed by a double scroll spring  33 . 
     For the motor control, the emitter  36  transmits contactless control signals to the sensor  12  which acts onto the rotating electronics. The fixed bearings  31  and  32  allow that the shaft  11  freely rotates and take over supporting forces which are caused by the whole opposite arrangement. Both ends of the hollow shaft  11  are situated inside closed spaces  37  and  37 ′, the sealing of the bearings  31 ,  32  being used for the protection of the brushes and of the unit emitter/receiver, whereby the housings  37 ,  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 rotors  1 ,  2  so that only a negligible friction moment is transmitted onto the support  37 , this moment coming from the brushes  33 ,  35  or the bearings  31 ,  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 rotors  1 ,  2  all 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 sensor  12 , by evaluation of the voltage and of the current on the brushes  33 ,  34  of 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 rotors  1 ,  2  can 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 devices  19 ,  29  which are driven by the rotors  1  and  2 , 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 rotor  1  drives two axial ventilator stages b and d with blades  18  which rotate in a direction, the inner rotor  2  driving the stage a or the stage c over the foot of the ventilator blades  29 , the stage c being fixed to the stage a over a simultaneously rotating cylindrical tube  27 . 
     The wall (the carrier)  38  which separates the overpressure spaces (P) or the underpressure spaces (J) can be configured as an extension of the housings of the bearings  31 ,  32  or of the brushes  33 ,  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 tube  27 . 
     For applications which require a high throughput for a low pressure, the alternative of an opposite motor with two ventilators according to  FIGS. 5   a, b  is advantageous (schematic representation and motor cross section). 
     The motor according to  FIG. 5   b  (driving gear arrangement, see  FIG. 5   a ) shows the configuration of two rotors as in  FIG. 1   a , the bearing arrangement corresponding to  FIG. 1   b . Here, the outer rotor  1  drives the blades  19  of a ventilator and the inner rotor  2  drives a laterally offset placed ventilator  29  by means of the belt  241  so that both ventilators work parallel the one besides the other. The transmission ratio of the belt drive  241  driven by the inner rotor  2  over the belt wheel (flange)  24  can 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. 6  shows two radial blowers  19 ,  29 , each one with a spiral blower, which are driven by the rotors  1  and  2  according to the invention. In  FIG. 7 , there is an alternative with two radially concentrical blowers  19 ,  29  which are driven by the rotors  1 ,  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.