ELECTRONICALLY COMMUTATED MOTOR

Information

  • Patent Application
  • 20070182261
  • Publication Number
    20070182261
  • Date Filed
    January 30, 2007
    17 years ago
  • Date Published
    August 09, 2007
    17 years ago
Abstract
For many applications, it is desirable to use fans which weigh less than 30 grams and are driven by electric motors not more than a few centimeters in size. Mass-producing products this small, which nevertheless must be extremely reliable, poses unique manufacturing challenges, which are best overcome by an improved structure which is susceptible to automation. Preferably, the fan motor is electronically commutated and has an internal stator (50) and an external rotor (22) supported on a central rotor shaft (34). The shaft is journaled within a bearing tube (70) supporting first and second rotor bearings (72, 76). By injection-molding the bearing tube (70) with first and second axial extensions (90′, 90″), the extensions can hold the bearings in place and insure uniform manufacturing quality and a desirably long service life. One of the extensions can also be shaped to abut against a circuit board (46) which supports components which control commutation.
Description

BRIEF FIGURE DESCRIPTION

Further details and advantageous refinements of the invention are evident from the exemplifying embodiments, in no way to be understood as a limitation of the invention, that are described below and depicted in the drawings. In the drawings:



FIG. 1 is a longitudinal section through a fan that is driven by a miniature or subminiature motor according to an embodiment of the invention;



FIG. 2 is a greatly enlarged top view of the hub of the fan of FIG. 1;



FIG. 3 is a longitudinal section, shown in perspective, through the air-directing tube of the fan of FIG. 1, with a depiction (likewise in perspective) of the internal stator;



FIG. 4 is a perspective depiction of the internal stator of FIG. 1, with a circuit board and MOSFET (MOS Field Effect Transistor) 48 arranged thereon;



FIG. 5 is a side view of the internal stator of FIG. 4;



FIG. 6 is a sectioned view of the internal stator of FIG. 4 with one of the two roller bearings, and with a stator winding;



FIG. 7 is a sectioned view of the internal stator of FIG. 6 with both rolling bearings;



FIG. 8 is a side view of the internal stator of FIG. 1 with injection-embedded connector elements 96;



FIG. 9 is a top view of the internal stator of FIG. 8, looking in the direction of arrow IX of FIG. 8;



FIG. 10 is a section looking along line X-X of FIG. 9;



FIG. 11 is a section looking along line XI-XI of FIG. 9;



FIG. 12 is a perspective depiction of the internal stator of FIG. 4 at approximately actual size; and



FIG. 13 is a longitudinal section through the fan of FIG. 1, at approximately actual size.


Claims
  • 1. An electronically commutated motor (21), comprising: a permanent-magnet external rotor (22) having a rotor shaft (34);an internal stator (50) having a stator lamination stack (52) with stator poles (52′, 52″, 52″′, 52″″) between which slots (54′, 54″, 54″′, 54 ″″) are defined;a plastic coating (77) which extends through the slots (54′, 54 ″, 54 ″′, 54″″) and, together with the stator lamination stack (52), forms a bearing tube (70) for reception of at least one bearing (72, 76) for journaling of the rotor shaft (34),said bearing tube (70) being formed with a first axial extension (90′) configured to engage around, and thereby support, a first rotor bearing (72).
  • 2. The motor according to claim 1, wherein said first rotor bearing (72) is secured within said first axial extension (90′) by forming plastic material of said bearing tube around said first rotor bearing.
  • 3. The motor according to claim 1, wherein the plastic coating (77) forms, at a first end (71′) of the stator lamination stack (52), a first end layer (73′) formed with corresponding cutouts (56′, 56″, 56″′, 56″″) at axial ends of the slots (54′, 54″, 54″′, 54″″).
  • 4. The motor according to claim 1, wherein said first axial extension (90′) is formed with a first recess (91) serving to secure said first rotor bearing (72) therewithin.
  • 5. The motor according to claim 1, wherein the first axial extension (90′) is formed with a first shoulder (91′) and a second shoulder (91″) for securing said first rotor bearing in place.
  • 6. The motor according to claim 3, wherein the first rotor bearing (72) is a rolling bearing.
  • 7. The motor according to claim 4, wherein at least part of the outer ring (72″) of the first rolling bearing (72) is surrounded by the plastic of the first axial extension (90′).
  • 8. The motor according to claim 1, wherein the plastic coating (77) and the first axial extension (90′) are formed integrally.
  • 9. The motor according to claim 1, wherein the first rotor bearing (72) is anchored in plastic material of the first axial extension (90′).
  • 10. The motor according to claim 5, further comprising a circuit board (46) and whereinthe first axial extension (90′) has a third shoulder (95) against which said circuit board (46) abuts.
  • 11. The motor according to claim 10, further comprising connector elements (96′, 96″, 96″′), located on said third shoulder (95), for connecting a winding (97) wound on said internal stator (50).
  • 12. The motor according to claim 11, wherein the connector elements (96′, 96″, 96″′) are mounted in the third shoulder by forming plastic material of said shoulder (95) around said connector elements.
  • 13. The motor according to claim 11, wherein the connector elements (96′, 96″, 96″′) are bronze pins.
  • 14. The motor according to claim 1, wherein the plastic coating (77) forms, at a second end (71″) of the stator lamination stack (52), a second end layer (73″) formed with cutouts (58′, 58″, 58″′, 58″″) at axial ends of the slots (54′, 54″, 54″′, 54″″),said second end layer comprising a second axial extension (90″) formed with a second recess (93) for reception of a second bearing (76) for journaling of the rotor shaft (34).
  • 15. The motor according to claim 14, wherein the second bearing (76) is a rolling bearing.
  • 16. The motor according to claim 12, wherein the second bearing (76) has an outer ring (76″) which is press-fitted into the second recess (93).
  • 17. The motor according to claim 15, wherein the external rotor (22) comprises a rotor cup (24) that abuts against an inner ring (76′) of the second bearing (76).
  • 18. The motor according to claim 17, further comprising a compression spring (94), mounted between an abutment (92), formed at a first end (35) of said rotor shaft, and an inner ring (72′) of said first rotor bearing (72), said spring (94) urging said first ring (72) toward said second rotor bearing (76).
  • 19. A fan (20), driven by an electronically commutated motor (21), said motor comprising: a permanent-magnet external rotor (22) having a rotor shaft (34);an internal stator (50) having a stator lamination stack (52) with stator poles (52′, 52″, 52″′, 52″″) between which respective slots (54′, 54″, 54″′, 54″″) are defined;a plastic coating (77) which extends through the slots (54′, 54″, 54″′, 54″″) and, together with the stator lamination stack (52), forms a bearing tube (70) for reception of at least one bearing (72, 76) for journaling of the rotor shaft (34),said bearing tube (70) being formed with a first axial extension (90′) configured to engage around, and thereby support, a first rotor bearing (72), whereinthe rotor shaft (34) comprises, at a first end (35), an abutment (92) between which and an inner ring (72′) of the first rotor bearing (72) is provided an axially extending compression spring (94) that urges said inner ring (72′) in a direction toward a second rotor bearing (76).
  • 20. A fan (20) according to claim 19, further comprising a fan wheel (23) with fan blades (26) projecting therefrom in a configuration adapted to serve as an axial fan.
  • 21. A method of making an electronically commutated motor having an external rotor;an internal stator (50) having a lamination stack (52) with a plurality of poles, defining between them slots (54′, 54″, 54″′, 54″″),a plastic coating (77) extending through the slots and forming, together with the lamination stack (52), a bearing tube (70) supporting at least one rolling bearing (72, 76) for journaling a shaft (34) of said external rotor,comprising the step offixing said at least one rolling bearing in position, by molding material of said plastic coating (77) around said rolling bearing (72).
  • 22. The method of claim 21, wherein said fixing-in-position step comprises engaging opposite faces of said rolling bearing between a first shoulder (91′) and a second shoulder (91″) of said plastic coating (77).
  • 23. The method of claim 21, further comprising the steps of: guiding a first plastic injection tool through said stator lamination stack,supporting a first rolling bearing (72) between two plastic injection tools, andinjecting plastic to thereby form a plastic element engaging around said bearings.
  • 24. The method of claim 23, wherein said step of injecting plastic further comprises using first and second plastic injecting tools to seal off said rolling bearing before injection of plastic, thereby assuring that no plastic penetrates into said rolling bearing during plastic injection.
Priority Claims (1)
Number Date Country Kind
20 2006 002 068.3 Feb 2006 DE national