Abstract:
A field part of an electronically switched two-phase reluctance machine includes a plurality of individually wound U-shaped yoke assemblies. Each assembly includes winding carrying U-shaped magnets attached to a non-magnetic carrier frame. Each yoke assembly has winding connections which are interconnected by a form-defined, axially mountable electric conductor compound. Power conducting electric components are electrically connected to the electric connector compound as well.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to the winding carrying part of electronically switched reluctance machines with separate electromagnets. In the course of the specification, we shall call this part “field part” or “stator”. The reluctance machines are sometimes called SR (switched reluctance) machines. Such machines are known by the prior art from the international patent applications WO 96/09683 and WO 98/23024. The first document knows a reluctance machine which has no stator but two independent opposed rotors, the conventional stator becoming the outer rotor because of a special bearing. This rotor (field rotor), similar to a stator, can also be realized according to the teaching of this invention. 
     The invention offers technological solutions for the realization of the stator of common machines or of the field rotor of the double rotor machines with a particular structure. For other parts of these machines (rotor, bearing), sufficient methods of production are known by the prior art. Unlike conventional motors (see FIG.  1 ), the stator has four independent yokes  11  which are equipped with respectively two cantilever windings each which are to be produced separately. 
     However, these machines mentioned by the prior art, which are basically very simple with electromagnets which are to be set in separately have to be realized with appropriate manufacturing techniques in order to produce mechanically, for example, the numerous electric connections of the windings or to guarantee the observance of a constant air gap as small as possible. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The aim of this invention is to indicate possibilities how the basically unique winding carrying parts of these machines can be economically produced by observing the above mentioned requirements. 
     The aim of the invention is achieved according to the teaching of the main claim. The subclaims refer to detailed embodiments of the components necessary for the assembly of the stator. To simplify, we took as an example in the course of the specification a SR motor (FIG. 1, cross section), as described in the WO 96/09683, with four U-shaped yokes  11  made of bundles of laminations which carry a bifilar winding  112 - 113  made of metal bands which are here called U-shaped magnets  10 . 
     The ways to reach the aim which are described here can also be used for other configurations of SR machines by simply adapting. The windings  112 - 113  necessary to produce the U-shaped magnets  10  are wound from two metallic bands or wires with intermediate insulating foils (bifilar main winding  112  and secondary winding  113 ). Since the winding band unlike the usual copper band has a preferred bending direction and does not need to be insulated, the mechanical working out of the winding connections (for example by folding, stamping, ultrasonic welding) is considerably simplified. For the winding fabrication, the beginnings  112 A,  113 A of the bands are, for example, folded with intermediate mylar foils  115  to 90° and bored through in the folding area in order to thus be hung up on the winding core  116  (FIG.  2 ). As may be seen here, the winding core  116  has two moulded brackets  116  with clip hooks which insulate the beginnings of the main and of the secondary windings ( 112 A,  113 A) with each other. The latter penetrate into the bore hole  117  from the folding area of the beginnings of the bands, what allows the electrically/mechanically separate fixing of the two pilot bands  112 ,  113  opposite the wound core. The wound core  116  with a rectangular cross section can, as usually, have lateral edges for being wound with wire, these lateral edges being not necessary for the embodiment with winding bands (FIG.  2 ). 
     The wound core  116  will then be wound correspondingly to the number of windings in order to simultaneously wind the main winding ( 112 ) and the secondary winding  113 . The end of the winding will then be preliminarily fixed by means of the lateral brackets  116 ′ so that the windings do not spring back after having cut the winding band. Respectively two windings are connected in series. A parallel connection of the windings is also possible, for example when it is the matter to use the same windings for a voltage which is twice lower. The windings  112 - 113  pushed through on the left (D) and on the right (S) on the yoke  11  are operationally connected with each other (beginning  112  left, beginning  112  right, beginning  113  left, beginning  113  right). 
     With reference hereto, the beginnings of the windings bent parallel to the U-shaped limbs are folded once again in direction of the middle part of the U-shaped yoke  11  (FIG. 1 indicated by a fat dashed line, wound core not drawn). The left and right arriving overlapping beginnings  112 A,  113 A of the pilot bands  112  and  113  can be soldered or ultrasonically welded and thus be mechanically and electrically connected with each other. This action can take place before as well as after the mounting of the windings onto the U-shaped bundles of laminations  11 . The further electric connection of the band conductors connected in series  112  and  113  then takes place at the ends of the left or of the right winding. See FIG. 1 a  to FIG.  3 . For this purpose, their ends  112 B,  113 B are cut in the manner of a plug (bent or stamped) or (for example for wire windings) equipped with independent plug lugs. 
     The use of the U-shaped yokes  11  allows the use of a special winding with a lower resistance which results from a partial increase of the width or of the cross section of the winding band. The section of each winding which is situated between the U-shaped limbs has the usual width I which is a little smaller than the limb height, whereby the remaining winding with the height L can be considerably wider (Page B, FIG.  8 . Here on the left, the new winding type is drawn, the old one on the right for comparison, respectively only the first winding). This is possible because the winding band width here (pages A, C, D) is no longer limited by the depth of the U-shaped yoke  11 . The developed view of a winding (pages A, B, C, D) can be seen in FIG.  9 . Here, the beginnings of the winding are realized (as an example) by means of separate connecting parts  112 A′,  113 A′ (page A) which can be ultrasonically welded. In this way, for example an aluminium winding can be provided with copper connections easy to be soldered ( 112 A′). This winding type can be realized more easily on motors with a few windings and allows an increasing of the power yield or the reduction of the iron quantity (iron losses). For the same resistance or the same ampere turns compared with the embodiment with a constant cross section (FIG. 1 a ), yokes with shorter limbs, thus with less iron, can be used here. The magnet  10  consisting of an U-shaped yoke  11  with two windings  112 - 113  is the basic component for the production of the stator  1  according to the invention, see FIG.  3 . 
     FIG. 3 a  shows the U-shaped yoke  11  with pole faces  111  and lateral fixing grooves  15  which has been bundled from punched steel sheet by a method known from the prior art. FIG. 3 b  shows the yoke with two windings according to FIGS. 1 and 2 as before the extrusion operation. FIG. 3 c  shows the U-shaped magnet  10  which has been extruded, for example, with a thermoplast, at least one side of the electromagnet being provided with pole faces  111  which are turned to a movable part  2  (rotor) over an air gap. Here, fixed, spatially precisely fitted plug lugs  112 B- 113 B,  112 B′- 113 B′ are constituted by the ends of both windings. One side of the plug lug  112 B forms the connection with the main winding ( 112 ), the other  113 B with the secondary winding  113 . For this purpose, the tool must be configured in such a way that plastic is injected for reinforcement between the plug lugs  112 B- 113 B which are squeezed in the injection moulding matrix during the injection moulding process. With respect to the tool technique, it is easier to extrusion-die the bands  112 - 113  a few millimeters from the winding edge (height of the shoulder  118 ). The still free ends of the bands ( 112 B,  113 B) which remained bare (they were clamped in the tool) will be bent over the plastic shoulder like the end  113 B, see for example FIG. 3 c , in order to thus form the plug lugs. Because all magnets necessary for one or several machine types are identical, they can be mass-produced at low costs (automatized production). The mechanically easy to handle U-shaped magnet  10  can be inserted/fixed in a frame  5  in order to form the stator  1 , see FIG. 4 b . For most of the motors (of the invention), the fixing to the frame  5  thus takes place over the outer corners of the U-shaped magnets in the area of the stator poles  111 , thus in immediate air gap proximity so that the windings remain on the outside, even if the rotor space  20  is connected. This is desirable, all the more since dirt particles could block the rotor  2 . This new mechanical construction also allows for a better cooling. Moreover, short fixing ways are thus possible between the rotor pole faces ( 121 ) or the stator pole faces  111  which allow a better observance of the very important narrow tolerances in the air gap area. FIG. 5 schematically shows with fat indicated lines a comparison of the length of the fixing ways (from bearing to bearing) between the rotor poles  121  and the stator poles  111  for common motors (left) or for a motor according to the invention (right). For common motors (left), the windings ( 113 ) are under the end shields (fett indicated line). The motor frame (FIG. 4) fixes the yokes  11  of the magnets  10  and positions the stator  1  and the corresponding components with respect to the rotor  2 . In the simplest form, it consists of a basic frame  5 ′ with columns  53 . In the embodiment for field rotors of statorless machines, this frame  5  is configured as symmetrical as possible and without balance error (like, for example, in FIG. 4 c ), since it rotates with the four U-shaped magnets  10 . It is constructed in this way so that the motor is sufficiently secured against extraction forces (caused by the centrifugal force) of the U-shaped magnets  10 . The motor frame  5  has mounting shoulders or nests for this purpose which allow (alternative according to FIG. 4 c ) that the electric parts are positioned exactly on the flange  5 ′. The frame is preferably diecasted from an aluminium alloy. 
     The frame  5  has openings  51  in which the ends of the U-shaped yokes  11  are inserted, the lateral walls thereof having for example half-round axially aligned grooves  52  which are opposite other half-round grooves  15  which are made in the outer corners of the U-shaped magnets  10 , see FIG.  4 . The four openings  51  are formed by four columns  53  which run from the front end shield to the rear (removable) end shield. On the inner sides  54  of these columns, the fixing of the U-shaped yokes  11  is carried out by appropriate methods, as follows. As can be seen in FIG. 4, left half (quadrant C and D), the magnets  10  can be inserted vertically to the plane of the drawing between the two columns  53 C,  53 D. The half-round webs  531 C,  531 D engage in the lateral fixing grooves  15  of the U-shaped magnets  10 . However, this requires, because of the tolerances, a high-accuracy fabrication. 
     In order to fix the U-shaped yokes  11  free from backlash, it is possible to spread out the columns  53  when mounting. For this purpose, the basic plate of the frame  5  has for example four wedge-shaped notches  58 . These notches will be widened during the assembly with wedges  7  so that the columns  53  spread approximately 0.1 mm outwards (corners dashed in the left drawing half). Thus, the yokes  11  can be inserted (with clearance) more easily. The columns  53  which spring back tense the yokes  11  free from backlash, when the wedges  7  are removed. Due to this method, the magnets can however only be mounted in axial direction and the upper ends of the columns  53  are free. The frame  5  can thus be closed with a flat rectangular end shield over the bore holes  532 , the columns  53  having the length of the bundle of laminations of an U-shaped yoke. It is also possible to use two half frames which are preferably identical, as in FIG. 4 b , where the four columns  53  are half as long as the bundles of laminations so that the yokes  11 , or the rotor, are clamped between the two, “half frames”, thus without separate end shield. 
     A construction with two half frames is also possible, each half frame being equipped with two columns  53  each (alternative 1, columns A and C, alternative 2 columns A and B) which have the length of the bundle of laminations. An appropriate assembly can also be achieved by pushing together the two half frames over the four yokes with an offset angle (about 90° or 190° depending on alternative 1 or 2). A higher assembly accuracy, even with rough toleranced (cheap) parts, can be achieved by means of a tolerance compensating method with so-called “liquid rivets”. 
     Due to the curing of the “liquid rivets”, parts with rough tolerances can be mutually fixed precisely in any position in order to respect narrow tolerances at a decisive point when assembling. For this purpose, the method is as follows. 
     A calibrating roll  24 , the outer diameter of which is bigger than the rotor diameter by the air gap dimension and which is centered over the bearing  25 , is inserted in the rotor opening  20 . The U-shaped yokes  11  are radially pushed into the motor frame  5 , for example the one after the other from the same direction (by gradual torsion of the motor frame  5  per step of assembly). Moreover, the four columns  53  of the frame  5  can also be connected above the yokes  11  by a ring (flange ( 5 ″) which allows the removal of the calibrating roll and the insertion of the rotor (FIG. 4 c ). With an appropriate device, all U-shaped magnets  10  are then pressed with the pole faces against the calibrating roll  24  and immovably fixed in this position by injection of a zinc alloy in the opposite half-round grooves  52 ,  15 . Instead of the zinc alloy, any hardenable material may be injected. For the assembly of the magnets  10 , instead of pressing from outside, their electromagnetic retention force can be used in case these magnets are flown through by current, whereby the calibrating roll  24  must then be magnetic. 
     In this way, not only a retention force can be achieved, but also the quality of the assembly can be checked. If one of the magnets  10  does not correctly sit close to the calibrating roll (for example because of the dirt accumulation on the pole faces) or if there is a winding connection, the reluctance of this magnetic circuit differs from a predetermined value what can be checked over the course of the voltage variation in case of a quick current variation. So, it is possible not only to simplify the assembly but also to check the quality of the mechanical electric properties of one magnet or of all magnets and of their connections. As may be seen in the right half of FIG. 4, in the quadrants A and B, see detail “Z”, it is not necessary here that the half grooves  15 ,  52  exactly correspond with each other. When the pole faces  111  are in the optimal functional position at the stop with the roll  24 , the half-round grooves  15 ,  52  can be offset by a distance d which results from the tolerance wedges. The injected hardenable material (zinc alloy, plastic, resin) fills the hatched space and so forms a bolt after hardening, whereby a tolerance compensation takes place. It is also conceivable to quickly inject a pin softened by heating in the grooves  52 - 15  between the U-shaped magnets  10  and the frame  5  and to immediately upset it (in plastic state) with a drift so that it fills the existing hollow spaces  52   15  like the liquid rivet. It is also possible to widen an extensible small tube by means of an inner pressure which locks the magnets ( 10 ) against the frame  5  in the art of a laterally extendible bolt. It is also possible to realize a fixing with fixing components (pins, screws). Hereby, however narrow tolerances must be worked with because the tolerance adaptation to a calibrating roll does not take place any longer. 
     After having removed the calibrated bumper roll  24 , the pole faces  111  of the U-shaped magnets define exactly the diameter of the rotor space  20  and thus the exact observance of the air gap. The motor is fixed to the frame  5 . Additionally, the motor frame  5  serves, for example in the area of the flange  5 ″, as a cooler for the transistors  21  and the power diodes  22 . In special embodiments, extensions of this frame can be configured as motor casing or as pump case. In the same way, this frame  5  can be formed as an extension of another body (gearbox body, pump set etc.). 
     FIGS. 4 b, c  show perspective views of two alternatives of the frame  5 , the c-alternative being provided for the radial assembly of the U-shaped magnets. 
     The connection of the plug lugs  112 B- 113 B of all U-shaped magnets with each other takes place, considering the high currents which these machines have, especially with low voltage (motor vehicle applications), by means of a conductor compound  6 , see FIG. 6, which is produced at low cost by punching or laser cutting. This conductor compound  6  produced from metal sheet conductors  61  (copper, aluminum or brass) with a thickness in the mm range and an insulating support  62 , should connect electrically all plug lugs  112 B,  113 B of all U-shaped yokes  10  at the same time, and eventually other high voltage conducting parts. The electric contact with the plug lugs  112 B,  113 B of the U-shaped magnets  10  can take place over welded, soldered or crimp connections or by pressure. The conductor paths  61  of the compound are similar to the conductor paths of an usual printed circuit and must be punched instead of being engraved only because of the material thickness. In order to fit or fix the conductor paths  61  on an insulating support  62 , it is appropriate to carry out the punching or cutting out operation in two separate phases, as follows (FIG.  6 ). 
     First, the separating paths  63  (drawn as fat black lines) in the not shaded area of the later conductor paths  61  are cut out from a material which is, for example, shaped as a strip so that the remaining conductor paths  61  due to connections to the edges  64  and inner areas  65  which are to be cut later do not fall out loosely from the plane of the original strip. 
     The conductor paths  61  which can still be handled with in all as an unit are fixed into an insulating support  62 , either by die extrusion with plastic (on one or two sides), clipping, ultrasonic riveting or sticking. 
     The excess edges  64  and inner areas  65  which still exist only for handling purposes are cut off and the contact lugs (FIG. 6 a ) bent or finished. Thus, the conductor compound is finished. FIG. 6 shows as an example a finished round conductor compound which is appropriate for a motor with four U-shaped magnets  10  with main windings ( 112 ) and secondary windings  113 . The punched conductor paths  61  are placed on an insulating support plate  62  with eight slits  67  for passing through the plug lugs  112 B,  113 B of the U-shaped magnets. The characters placed on their faces mean: 
     Ip=connections of the/between the sections of the main windings  112  (main current), 
     Ib=connections of the/between the sections of the secondary windings  113  (bypass current) 
     +−connection on the positive (plus) pole 
     −connection on the negative (minus) pole 
     G−connections of the gate electrode, 
     As the partial cross section, FIG. 6 a , shows, the ends of the conductor paths  61 B which are connected with the plug lugs  112 B,  113 B of the U-shaped magnets  10  can be bent obliquely upward so that they can contact the latter in the art of a plug-in connection. 
     A loop  61   b  of the connection of the main winding  113  can be brought to another plane, for example by pressing in order to serve, for example behind the Hall sensor  31 , as a magnetic feedback of the main current Ip. The conductor compound  61  can show on one side a printed card  66  on which the electronic control elements of the motor can be mounted. FIG. 7 shows a cross section through a motor, for example with a frame  5  as represented in FIG. 4 c , where the axial fitting of the conductor compound  6  and of other motor elements can be seen. The frame  5  has here a flange  5 ″, eventually with cooling ribs, what can serve as a cooler for motor heat or for the electronic components. The motor parts (rotor  2 , stator  1 , yokes  11 , Hall sensor  31 , conductor compound  6 , power switch  21 , windings  112 - 113 , transmitter magnet  32  etc.) have the reference numerals from the preceding pages. A round end shield  8  with ball bearing closes the rotor space after assembly of the rotor  2 . The frame according to FIG. 5 c  can preferably be used for the rotor of a machine with two independent rotors (see prior art), the frame ( 5 ) being then mounted on a hollow shaft and the magnets ( 10 ) being mounted without balance error and resistant to the centrifugal force. Thus, a motor is realized which is similar to the motor of FIG. 7, except the bearings and the current transmission (by slip rings). 
     The advantages of the construction according to the invention have been made clear in the course of the specification. Due to the extrusion coated magnets  10 , the motor does not need any casing under normal conditions and has particularly good electrical and thermal properties due to the band winding with high filling factors. Should it be necessary for the protection of the conductor compound plate  6  or for the protection of the whole motor or for the noise reduction, the motor can be placed entirely or partially (only the connections and the electronics, for example) in an appropriate casing. 
     FIG. 10 shows the cross section of a motor/blower unit (for example for vacuum cleaners) with particular thermal characteristics which is possible by using the multifunctional frame  5  in connection with other construction solutions. 
     A part of the heat which develops in the windings can be directly dissipated on the flange  5 ″ (with cooling ribs which are configured in an advantageous way for the flow). The lower side of the windings  112 ,  113  adheres to the flange  5 ″ and transmits the heat by direct contact or over a heat conducting layer. The frictional heat of the lower bearing is also supplied to the flange  5 ″ over the end shield feeding part  8 . The power switches  21  are directly connected with the conductor compound  6 , however dissipate the heat to a housing  9  which also dissipates the heat from the upper bearing over the frame  5 . 
     The housing  9  is constructed in such a way that it is in thermal connection with the yokes  11  and is annexed to the flange  5 ″ without a sealing. The connections  91  of the motor come out laterally from a flow casing  93  surrounding the motor by a tube-type line  92 . The medium (air, eventually with impurities, see fat arrows) sucked by the blower  94  through the opening  95  of the flow casing  93  scavenges and thus efficiently cools the housing  9  and the flange  5 ″ and thus the encapsulated motor. Here, dirt or water cannot penetrate into the motor, despite missing sealings because its housing  9  is situated inside a vacuum space (flow housing  93 ) so that a relative overpressure prevails in the motor space, all the more since clean air arrives into the motor space by the line  92 . 
     If openings  83  are made for example in the end shield  8 , a clean air cooling flow (thin arrows) can be purposefully led through the motor space, this flow mixing then with the unclean main air flow (fat arrows) at the outlet.