Patent Publication Number: US-2019199156-A1

Title: Stator of a three-phase electronically commutated dc motor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present patent application is based on, and claims priority from, German Application No. DE 10 2017 223 519.5, filed Dec. 21, 2017, which is incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
     The invention relates to a stator of a three-phase electronically commutated DC motor, having a stator core, an insulating material body and a coil wire. 
     (2) Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98 
     An important application of such stators is brushless DC motors for motor vehicles with a dual-voltage on-board power supply. In many applications, the usual 12V is adequate as a supply voltage. Due to the increase in the number of consumers with higher energy requirements, such as main cooling water pumps, the introduction of an on-board electrical system with a higher voltage level will be indispensable in the future. It is likely that a 48V on-board electrical system in parallel with the existing 12V electrical system will prevail. In principle, the higher voltage causes less power to be consumed by the individual consumers. In electric motors, this means that smaller coil wires with a smaller wire diameter can be used. These have a relatively thin insulating layer. Due to imperfections in the lacquer insulation or abrasion due to micro-vibrations, short circuits can arise between coil wires of different phases and thus of different voltage potentials. This would result in failure of the affected electric motor. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention relates to a stator of a three-phase electronically commutated DC motor, having a stator core, an insulating material body and a coil wire, wherein the stator core has a closed back iron and a plurality of stator poles pointing radially inwardly from the back iron, which contacts the insulating material body axially at the stator core, and covers both the back iron and also the stator poles. 
     The present invention is aimed at three-phase internal-rotor motors, which are wound by a needle-winding method, in particular as brushless DC motors having a diameter of about 40 to 80 mm and a power range between about 300W and about 2 kW. When winding the stators, it is advantageous if the complete stator can be wound continuously without interruption with a single coil wire. In installing the wire on the stator, as a rule, up to four wires are laid in parallel. Wire crossings cannot be avoided either in a compact design. There is therefore the risk of contacts and thus of short circuits. 
     An object of the invention is a stator for a brushless DC motor designed in such a way that it is designed for a 48V on-board electrical system, being especially compact and nevertheless reliably preventing coil wires of different phases from touching each other and an economical production process being used. 
     In order to ensure defined conditions and the smallest possible movements of the coil wires both in the stator coils and in the connecting lines between the coils and between the phases, attention should be paid to ensuring an adequate wire tension. The geometry of the insulating material body also plays an essential role in this. In the case of connecting wires laid in a circular path, it is relatively easy to achieve a wire installation which is always play-free. For this reason, it is provided that phase wire sections are laid in wire guidance contours, which run along a circular path. Here the wire guidance contours should be designed such that no contacts are possible between phase wire sections laid in parallel around an annular wire guidance region or between skewedly crossing phase wire sections. Due to a helical course of a section of the wire guidance contours it is possible to shift the axial position of the coil wire by a contour level and achieve a compact structure. 
     A reliable separation of phase wire sections is provided when each phase wire section is guided in its own wire guide contour. These are separated from each other by a wall and even with a faulty wire insulation assure a short-free operation. 
     Depending on requirements, the wire guidance contour may also be interrupted without departing from the scope of protection of the invention. This relates in particular to an external distal wire guidance contour at the end of which a phase wire section is guided radially inwardly to a stator pole. 
     It is intended that the coil wires be always under mechanical tensile stress. This is effected on the one hand by the geometry of the wire guidance contours, which have a substantially circular course, as well as by a defined force with which the coil wire is kept under tension during the winding process. Here, areas with openings around the coil wire are to be avoided. In the optimal case phase wire sections run without play within the wire guidance contours. In this way no vibrations can arise and consequently no wire breaks will occur. 
     At various locations around the wire guidance region it may be necessary to depart from the circular shape of the wire guidance contours. This is often necessary in crossing areas or in places where other technical obstacles require the wire to be diverted. 
     In order nevertheless to maintain wire tension as strong as possible, this diversion is provided in the form of a chord, if at all possible, with continuous transitions between the circle segment and the chord section. Alternatively, a further circle segment with a significantly greater radius than the circumference may be provided instead of a chord section. In this case, wire tension is largely preserved. 
     Particularly advantageous are the above-mentioned deviations from the circular shape in regions in which an axially extending phase wire section skewedly passes radially externally a phase wire section of a different phase, said section running circumferentially. In the case of a wire guide contour optimally adapted to the wire diameter, short circuits can thereby be reliably avoided. 
     It is preferably provided that all axially extending phase wire sections skewedly pass radially externally a phase wire section of a different phase, said section running circumferentially. This is necessary when the phase wire sections are laid between the coils of the first winding phase in a first wire guidance contour, said contour being located at the outer axial end of the wire guidance region facing away from the stator, the second phase wire sections in an adjacent middle wire guidance contour and the third phase wire sections in a wire guidance contour close to the stator. 
     For the winding operation it is intended that the insulating material body have radially projecting permanent, removable or reversible deflectors. Permanent deflectors are to be provided when sufficient installation space can be made available. In a more compact design, the deflectors can after the winding process be severed, folded or bent, depending on the geometric design. This usually requires an additional process step, unless bending is performed during assembly of a housing. 
     It is intended here that a circumferentially laid phase wire section is guided at a deflector in an axial direction and crosses at least one axially adjacent wire guidance contour, which at this point has a non-circular section. The phase wire section guided in the axial direction here moves away from the stator. In this way the phase wire section running circumferentially will always deviate away from contact with a phase wire section running axially. The phase wire section running axially must also be guided by means of a wall between the phase wire sections, said wall having no recess. It is also conceivable that, in order to avoid an increase in diameter, the phase wire section running axially also be sunk into the wall between the wire guidance sections. In this case the deviation from the circular shape of the adjacent wire guidance contour would have to be implemented correspondingly more clearly in order to ensure a sufficient distance between the various phase wire sections. 
     A special feature of this invention is that at least some of the wire deflectors project radially between two wire guide contours. In this way, the phase wire sections can be laid more flexibly, so that it is also possible in a simplified manner to wind the complete stator continuously using a single coil wire. 
     Since the wire guide contours lie close together, the wire deflectors projecting radially between the wire guidance contours are radial extensions of walls between the wire guidance contours. So that the phase wire sections can be laid in the wire guidance contours it makes sense for the deflectors to be formed flat, like the walls. 
     In the embodiment of the insulating material body according to the invention, it is not necessary for the wire guidance contours to have slot-like wire feedthroughs passing through the wire guidance region. This permits a more stable design for the wire guidance region and a higher wire tension can be achieved. 
     It may be necessary for the insulating material body to have centering contours which correspond to corresponding contours of the stator and/or of a housing, wherein the centering contours have the shape of a recess. These centering contours hold the stator centered with respect to a housing or provide anti-rotation protection or serve for better positional assignment. Even on such centering contours, the insulation of the phase wire sections must not be impaired, so for this reason it is also provided here for the wire guidance contours in the region of the centering contours to have a recess whose depth is dimensioned such that a phase wire section can be completely accommodated therein, without protruding into the region of the centering contours. 
     Depending on space requirements, different embodiments of the insulating material body may be useful. If the diameter of the stator and thus of the DC motor is to be kept low, it is expedient for the annular wire guidance region to axially extend the insulating material body. If the axial installation space is limited, the annular wire guidance region can also radially expand the insulating material body. 
     The terminal projections in each case connect axially to the wire guidance region. These are designed in such a way as to have shaft-like housing contours for accommodating an insulation displacement contact, wherein slot-like radial recesses in the shaft wall are provided for receiving a radial phase wire section. 
     It is appropriately provided for limiting means to be present axially on the wire guidance region which are integral with the insulating material body and which prevent the radial phase wire sections from shifting or deflecting in the circumferential direction. As a result, the degrees of freedom of the wire become restricted and the oscillation tendency significantly reduced. 
     For structural reasons it is expedient for a wire guidance contour to have a leadout contour in one end region, whereby the wire guidance contour merges steplessly into a guide-free section of the wire guidance region. Before the leadout contour, flat deflectors are provided which facilitate a wire deflection. The wire guide contour then ends and merges with the leadout contour. The deflectors for the phase wire sections can be removed after winding, since as a result of the wire tension the coil wire can no longer escape from the wire guidance contours. 
     In many applications, such as electric oil pumps, a printed circuit board for electrically driving the motor is located near the winding circuit. In order to optimize the printed circuit board layout, it is advantageous for the phase connections to lie close to one another, preferably in an angular range of not more than 120°. 
     The stator and an electric motor with this stator are preferably designed for an on-board power supply voltage of 48V, with a voltage range of 24V to 60V or 36V to 60V or 40V to 60V. 
     The stator is designed for an on-board power supply voltage of 36V, with a voltage range of 24V to 48V or for an on-board power supply voltage of 110V, with a voltage range of 90V to 150V. 
     It is further provided that the energy for energizing the stator is supplied by a direct current source, by an alternating current source, by a three-phase current source or by a pulsed direct current. 
     The stator has a diameter in the range between 40 and 80 mm or between 40 and 160 mm or between 40 and 200 mm. Finally, the stator and an electric motor with this stator are designed for a power range between 300W and 2 kW or between 300W and 4 kW or between 300W and 6 kW. In addition, an electric motor with a stator according to any one of the preceding claims is claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The exemplary embodiments of the invention are subsequently further explained, based on the drawings. The following is shown: 
         FIG. 1  is a view of a stator from the prior art, 
         FIG. 2  is a first embodiment of a stator according to the invention, 
         FIG. 3  is a side view of an insulating material body with wire installed, 
         FIG. 4  is a detail of the insulating material body with intersecting wire feeds, 
         FIG. 5  is the stator wound with a first phase, 
         FIG. 6  is the stator wound with the first and a second phase, 
         FIG. 7  is the stator wound with the first, the second and a third phase, 
         FIG. 8  is a further detail showing deflectors, 
         FIG. 9  is a partial view of the insulating material body with deflectors, 
         FIG. 10  is a second embodiment of stator according to the invention with a neutral point contact, 
       and 
         FIG. 11  is a winding diagram of the three phases. 
     
    
    
     Note: The reference numbers with index and the corresponding reference numbers without index refer to details with the same name in the drawings and the drawing description. The reference number list contains only reference numbers without index for the sake of simplicity. 
     DETAILED DESCRIPTION OF THE INVENTION 
     In describing preferred embodiments of the present invention illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the invention is not intended to be limited to the specific terminology so selected, and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner to accomplish a similar purpose. 
       FIG. 1  shows a prior art stator  1   a  with a stator core  2   a  having a back iron  3   a  and stator poles  4   a , an insulating material body  5   a  and a coil wire  6   a . Although the insulating body  5   a  does include a wire guidance region  10   a , the insulating body does not have adequate wire guidance contours. The up to four parallel connecting wires between the phases (phase wire sections  7   a ) may touch each other. The stator of a 12V motor, whose wire diameter is relatively large, is concerned here. Accordingly, the wire insulation is also relatively thick-walled and is generally adequate. Wire crossings are avoided in that the wire guidance region  10   a  is often interrupted by slots. The wall thickness must thus be increased accordingly in order to obtain sufficient stability. 
       FIG. 2  shows a 3D illustration of a first embodiment of the stator  1   c  according to the invention, with a back iron  2   c , radially inwardly projecting stator poles  4   c , an insulating material body  5   c , a coil wire  6   c  and an insulating cap  20   c  without a wire guidance function. The insulating material body  5   c  has an outer ring  21   c  pushed over the back iron  2   c , an axially adjoining wire guidance region  10   c  and axially adjoining terminal projections  34   c ,  35   c ,  36   c ,  37   c . The wire guidance region  10   c  has wire guidance contours  12   c  in the form of grooves formed in the wire guidance region  10   c  and separated from each other by walls  22   c . The terminal projections  34   c ,  35   c ,  36   c ,  37   c  have shaft walls  23   c , each forming a receiving shaft  24   c  for an insulation displacement contact. Two shaft walls  23   c  of the connecting projections  34   c ,  35   c ,  36   c ,  37   c  have in each case slot-like recesses  16   c  which serve to receive radially laid phase wire sections  8   c.    
     Limiting means  25   c  that are integral with the insulating material body  5   c  axially adjoin the wire guidance region  10   c  and prevent radial phase wire sections  8   c  from shifting or deflecting, said limiting means leading not into one of the slot-like recesses  16   c  but rather to a coil of a stator pole  4   c . To enable reliable installation of the coil wire during the winding operation, in particular when laying the circumferential wire section  7   c  by 90° in an axial direction (axial phase wire section  9   c ), flat deflectors  11   c  and cylindrical deflectors  15   c  are provided. If the deflectors  11   c  are arranged between two wire guidance contours  12   c , they will be flat like the wall  22   c  and formed as an extension thereof. The flat geometry is required in order to enable installation of the phase wire section  7   c  into the wire guidance contour  12 . Cylindrical deflectors  15   c  may be provided that are wider than the wall  22   c  when they are arranged at the axially outer end of the wire guidance region  10   c . Furthermore, a helical section  19   c  of wire guidance contours  12  can be seen. 
       FIG. 3  shows a side view of the insulating material body  5   c  according to  FIG. 2  with coil wire  6   c  laid thereon, in particular phase wire sections  7   c . In one section  19   c , a helical course of wire guide contours  12   c  can be seen here more clearly than in  FIG. 2 , this being provided in a transition region from a first to a second phase as well as from a second to a third phase. Furthermore, the wire guidance contours  12   c , the walls  22   c  between the wire guidance contours  12   c , the radially arranged flat deflectors  11   c , the cylindrical deflectors  15   c , the axially disposed limiting means  25   c  and the axially disposed terminal projections  16   c  can be seen to which the axially extending phase wire section  9   c  leads and in which the radially extending phase wire section  8   c  lies in the slot-like recess  16   c . There are two single terminal projections  35   c ,  36   c  present and a double terminal projection  34   c ,  37   c  which receives the start and the end of the coil wire  6   c . The limiting means  25   c  have oblique insertion regions  26   c.    
       FIG. 4  shows a detail of the insulating material body  5   c , with the wire guidance contours  12   c , the walls  22   c , the flat deflectors  11   c , the limiting means  25   c , with the oblique insertion regions  26   c , the phase wire sections  7   c  running along a circumferential circle, the axially extending phase wire sections  9   c  and the radially extending phase wire sections  8   c . The narrow contour of the flat deflectors  11   c , which represent a radial extension of the walls  12   c , can be clearly seen. The wire guidance contours  12   c  are groove-like recesses in the outer circumference of the insulating material body  5   c . In the angular sectors, in which the axially extending phase wire sections skewedly cross each other, the phase wire sections are recessed in a chord-like configuration in order to ensure a safe distance from the crossing phase wire section. To prevent the latter from causing any increase in radial diameter, a wall  22   c  with a recess  27   c  is also provided. The recess  27   c  and the recess of the wire guidance contour are matched such that an adequate distance between the crossing phase wire sections is always ensured. 
       FIG. 5  shows the stator  1   c  wound with a first phase. The stator  1   c  has nine poles, with three poles in each case belonging to one phase. The coil wire  6   c  passes radially inwards through the slot-like recess  16   c  of the first terminal projection  34   c  to a first stator pole  4   c , there forms the first coil  28   c  and is guided radially outwardly through a first opening  31   c  in the outer wall  22   c  and into the first wire guidance contour  12   c . The opening  31   c  also extends axially through the wire guidance region  10   c . Since the coil wire  6   c  cannot escape at the first opening  31   c  no additional deflector is required. The coil wire  6   c  is guided by the wire guidance contour  12   c  at a first edge of a second opening  32   c  to a further stator pole, where it forms the second coil  29   c . The coil wire  6   c  is guided radially outwardly from the second coil  29   c  at a second edge of the second opening  32   c  and guided back to the outer wire guidance contour  12  and up to a third opening  33   c . The coil wire  6   c  passes through the third opening  33   c  radially inwardly to a further stator pole and there forms the third coil  30   c . From the third coil  30   c  the coil wire  6   c  is guided axially to the second terminal projection  35   c  (not shown in  FIG. 5 ). The first phase of the coil wire  6   c  is thus laid. 
       FIG. 6  shows the stator  1   c  wound with the first and second phases. The transition from the first to the second phase is at the second terminal projection  35   c . From the second terminal projection  35   c  the coil wire  6   c  runs a short way axially to a cylindrical deflector  15   c  and from there, bending by about 90°, into the helical section  19  of the wire guidance contour  12   c . As a result, the already occupied axially outer wire guidance contour  12   c  is bypassed. The helical section  19   c  passes into a wire guidance contour  12   c  parallel to the phase wire section  7   c  of the first phase ( FIG. 5 ). At a flat deflector  11   c  the coil wire  6   c  is bent away at a right angle, guided axially and then radially over the outer wall  22   c  between two limiting means  25   c  and onward to a further stator pole. There the coil wire  6   c  forms the fourth coil  38   c . From there the coil wire  6   c  runs again through two limiting means  25   c  back to the second wire guidance contour  12   c  (concealed) and from there in the same way onward through further limiting means  25   c  to a stator pole  4   c . There the coil wire  6   c  forms a fifth coil  39   c . From the fifth coil the coil wire  6   c  runs through further limiting means  25   c  again outwardly into the second wire guidance contour  12   c  (partially concealed), around a flat deflector  11   c  and then onward in the second wire guidance contour  12   c . In the same manner a sixth coil  40   c  is formed. From there, the second phase is terminated with the passage through the third terminal projection  36   c  (not shown here). 
       FIG. 7  shows the stator  1   c  fully wound with three phases. From the third terminal projection  39   c  the coil wire  6   c  runs past a flat deflector  11   c  into a second helical section  19   c  of the wire guidance contour  12   c , past the first coil  28   c  and the fourth coil  38   c , around a deflector  11   c  (concealed) and through limiting means  25   c  to a further stator pole  4   c  to form a seventh coil  41   c . From the seventh coil  41   c  the coil wire  6   c  runs radially outwardly and via a third wire guidance contour  12   c  which runs circumferentially to a flat deflector  11   c  and through limiting means  25   c  inwardly to a further stator pole  4   c  and there forms the eighth coil  42   c . From the eighth coil  42   c  the coil wire  6   c  extends further radially inwardly around a flat deflector  11   c  via the third wire guide contour, then around a further flat deflector  11   c  to a further stator pole and there forms a ninth coil  43   c . From the ninth coil  43   c , the coil wire  6   c  runs directly to a fourth terminal projection  37   c  which together with the first terminal projection  34   c  forms a double terminal projection. In the present example the stator is delta-connected, the coil start therefore is connected to the coil end. 
       FIG. 8  shows another detail of the insulating material body  5   c , with the wire guidance contours  12   c , the walls  22   c , the flat deflector  11   c , the phase wire section  7   c  running along a circumference, the axially extending phase wire section  9   c  and predetermined breaking points  44   c . The predetermined breaking points are of a notch-shaped design so that the flat deflectors  11   c  can be easily removed. 
       FIG. 9  shows a partial view of the insulating material body  5   c  with the deflectors  11   c , the wire guidance contours  12   c , the walls  22   c , a centering contour  14   c , chord-like recesses  48   c , the recesses  27   c , the predetermined breaking points  44   c  and the limiting means  25   c . The chord-like recesses  48   c  serve at this point to lay the phase wire sections around the spatial region of centering means. The centering contour  14   c  also continues in the region of the walls  22   c.    
       FIG. 10  shows a wound stator  1   b  with a neutral-point contact  45   b . For this purpose, two additional terminal projections  46   b  and  47   b  are provided in order to connect the three phases to each another at a neutral point. In addition, the structure and the winding of the stator are similar to a stator with a delta connection. 
       FIG. 11  shows a winding diagram for the three phases A, B, C of the stator. The entire stator is wound with a single coil wire  6 , starting with phase A by winding around a first stator pole  4 , passing the coil wire onward through phase wire sections  7  past two unwound stator poles to a second stator pole  4  of phase A and in the same way to a third stator pole. Phase B starts with a pole offset from the starting point of the first phase and is continued in the same manner as in phase A. Phase C starts with a stator pole offset from the starting point of phase B and is wound analogously to phases A and B. The end point of phase C coincides with the starting point of phase A, resulting in a delta connection. 
     Modifications and variations of the above-described embodiments of the present invention are possible, as appreciated by those skilled in the art in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims and their equivalents, the invention may be practiced otherwise than as specifically described. 
     LIST OF REFERENCE SYMBOLS 
     
         
           1  Stator 
           2  Stator core 
           3  Back iron 
           4  Stator pole 
           5  Insulation body 
           6  Coil wire 
           7  Phase wire section 
           8  Radial phase wire section 
           9  Axial phase wire section 
           10  Wire guidance region 
           11  Flat deflector 
           12  Wire guidance contour 
           13  Deviating section 
           14  Centering contour 
           15  Cylindrical deflector 
           16  Slot-like recess 
           17  Leadout contour 
           18  Guide-free section 
           19  Helical section 
           20  Insulating cap 
           21  Outer ring 
           22  Wall 
           23  Shaft wall 
           24  Receiving shaft 
           25  Limiting means 
           26  Insertion area 
           27  Recess 
           28  First coil 
           29  Second coil 
           30  Third coil 
           31  First opening 
           32  Second opening 
           33  Third opening 
           34  First terminal projection 
           35  Second terminal projection 
           36  Third terminal projection 
           37  Fourth terminal projection 
           38  Fourth coil 
           39  Fifth coil 
           40  Sixth coil 
           41  Seventh coil 
           42  Eighth coil 
           43  Ninth coil 
           44  Predetermined breaking point 
           45  Neutral-point contact 
           46  Fifth terminal projection 
           47  Sixth terminal projection 
           48  Chord-like recess