U.S. patent number RE34,456 [Application Number 07/659,662] was granted by the patent office on 1993-11-23 for miniature axial fan.
This patent grant is currently assigned to Papst Motoren. Invention is credited to Siegfried Harmsen, Gunter Wrobel.
United States Patent |
RE34,456 |
Harmsen , et al. |
November 23, 1993 |
**Please see images for:
( Certificate of Correction ) ** |
Miniature axial fan
Abstract
The invention relates to a miniature axial fan particularly of
an axially compact construction, having a central motor driving a
rotor disk with a housing surrounding the rotor disk in which an
interior housing wall on the inflow side is cylindrical and extends
past the axial center of the housing and then this cylinder wall
expands outwardly to the outlet side of the housing to produce an
enlargement of the flow cross-section. The housing has webs
extending inwardly from the outlet side of the housing that carry
the central driving motor with the rotor disk. A number of blades
are mounted on the rotor disk which numbers differs from the number
of webs.
Inventors: |
Harmsen; Siegfried (Georgen,
DE), Wrobel; Gunter (Villingen, DE) |
Assignee: |
Papst Motoren
(DE)
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Family
ID: |
27433453 |
Appl.
No.: |
07/659,662 |
Filed: |
February 21, 1991 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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928476 |
Nov 10, 1986 |
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Reissue of: |
221947 |
Jul 6, 1988 |
04806081 |
Feb 21, 1989 |
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Foreign Application Priority Data
Current U.S.
Class: |
417/354;
417/423.14 |
Current CPC
Class: |
F04D
25/0613 (20130101); F04D 29/545 (20130101); F04D
29/526 (20130101); F04D 29/384 (20130101) |
Current International
Class: |
F04D
25/02 (20060101); F04D 25/06 (20060101); F04D
29/40 (20060101); F04D 29/52 (20060101); F04D
29/38 (20060101); F04D 29/54 (20060101); F04D
025/00 () |
Field of
Search: |
;417/354,353,352,423.15,423.14,424.1 ;415/181,119,200,207,220 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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100078 |
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Jul 1983 |
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EP |
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2252415 |
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May 1973 |
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DE |
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3118289 |
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Mar 1982 |
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DE |
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1110068 |
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Feb 1956 |
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FR |
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348501 |
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Oct 1960 |
|
CH |
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519032 |
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Mar 1940 |
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GB |
|
1154812 |
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Jun 1969 |
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GB |
|
1439513 |
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Jun 1976 |
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GB |
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1438313 |
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Sep 1976 |
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GB |
|
2014658 |
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Aug 1979 |
|
GB |
|
2059859 |
|
Apr 1981 |
|
GB |
|
2080046 |
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Jan 1982 |
|
GB |
|
2133082 |
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Jul 1984 |
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GB |
|
Primary Examiner: Bertsch; Richard A.
Assistant Examiner: Freay; Charles
Attorney, Agent or Firm: Barnes & Thornburg
Parent Case Text
This is a continuation of application Ser. No. 928,476, filed Nov.
10, 1986, now abandoned.
Claims
We claim:
1. A miniature axial fan, particularly of an axially compact
construction, comprising:
a central motor driving a rotor disk, said rotor disk having a
diameter of not more than 60 mm;
a one-piece molded unitary housing surrounding said rotor disk and
including an inlet flow side being cylindrical with an
approximately constant diameter extending rearwardly to and over
the axial center of said housing;
said housing also including more than one web means on the outlet
side for holding said central motor and rotor disk and a square
flange plate means at the housing outlet side for defining the
configuration thereof;
said housing further including a fastening pillar means having a
continuous fastening bore which extends from said inlet side to
said outlet side of the housing, said fastening pillar extending
from the square flange plate at the outlet side to the inlet side
of the housing; and
wherein said rotor disk has a number of fan blades thereon which
number of blades differs from the number of web means.
2. A miniature axial fan according to claim 1, wherein said
one-piece unitary housing has an expanding cross-sectional area at
the outlet side by having said outlet flow side expand radially
outwardly along a downstream flow direction.
3. A miniature axial fan according to claim 2, wherein the
enlargement of the flow cross-section extends outwardly toward four
contour corners of the square flange plate means defining the
housing configuration in a way that increases in flow direction
toward the outlet, with a continuous increase in cross-section.
4. A miniature axial fan according to claim 1, wherein the housing
includes four web means arranged at centers of the square sides of
the housing flange plate for holding the central driving motor.
5. A miniature axial fan according to claim 1, wherein the number
of blades means cannot be divided evenly by the number of web
means.
6. A miniature axial fan according to claim 1 wherein the motor has
a rare earth metal magnet and said unitary housing also includes a
rotor hub housing that is reduced in disk hub .[.its.]. diameter in
steps for receiving the rotor in a press fit with an outside
diameter of the rotor disk hub approximately the same as an outside
diameter of the rotor hub housing.
7. A miniature fan according to claim 5 wherein there are seven
blade means and four web means.
8. A miniature fan according to claim 7 wherein the inlet end of
the blade means is set back 3 mm from the inlet side and the outlet
edge of the blade means is set a distance of 4 mm from the web
means.
9. A miniature fan according to claim 1, wherein the blade means
have a large adjusting angle (.alpha.) of 70.degree. to 90.degree.
at the outlet end as seen in a top view that is radial with respect
to the axis of rotation onto the blade, as the blade means first
bends slightly from the direction at the blade means end at the
inlet side and then this bend changes into a bend that becomes more
extensive up to an edge of the blade means at the outlet side.
10. A miniature fan according to claim 1, wherein there is an
exterior means that has a portion extending in a radial direction
and located at the inlet to the housing and wherein the portion
extending in a radial direction completely encloses a radially
extending portion of the rotor disk.
11. A miniature fan according to claim 1, wherein there is an
exterior means that has a portion extending from the inlet of the
housing toward the outlet of the housing which portion of the
exterior means completely encloses a portion of the rotor disk that
lies adjacent to root portions of the blades.
12. A miniature fan according to claim 10, wherein the exterior
means also has a portion extending from the inlet of the housing
toward the outlet of the housing which latter portion of the
exterior means completely encloses a portion of the rotor disk that
lies adjacent to root portions of the blades.
13. A miniature axial fan according to claim 1, wherein the rotor
disk has a diameter of 45 mm and the adjusting angle (.alpha.) is
about 80.degree..
14. A miniature axial fan according to claim 9, wherein the housing
has an outer configuration of a square with a square side length of
50 mm, and wherein the slight bend corresponds to a bending radius
(R 1) of about 60 mm, and the extensive bend (R 2) corresponds to a
bending radius of about 15 mm.
15. A miniature axial fan according to any one of claim 13, 4, 5,
14 and 1 wherein, the inlet end of the blade means are set back
from the inlet side by a few millimeters, and the outlet end of the
blade means are set at an axial distance to the web means of a few
millimeters.
16. A miniature axial fan according to any one of claims 13, 4, 5,
14 and 1 wherein the blade means do not overlap along the direction
of the flow of the fan and wherein the inlet end of the blade means
has a radius of about 4 mm.
17. A miniature axial fan according to any one of claims 13, 4, 5,
14 and 1 wherein the rotor disk hub has a diameter equal to at
least half the rotor disk length.
18. A miniature axial fan according to any of claim 13, 4, 5, 14
and 1 wherein a rotor disk has a housing hub which, in the area
tapers conically toward the inlet and wherein the rotor disk has a
diameter which is below 50 mm. .Iadd.
19. A miniature axial fan, particularly of an axially compact
construction, comprising;
a central motor driving a rotor disk,
a one-piece molded unitary housing surrounding said rotor disk and
including an inlet flow side extending rearwardly to an outlet flow
side;
said housing also including more than one web means for holding
said control motor and rotor disk;
a square flange plate means;
said housing further including a fastening pillar means having a
continuous fastening bore which extends from said square flange
plate and between said inlet flow side and said outlet flow side of
the housing; and
wherein said rotor disk has a number of fan blades thereon, which
number of blades differs from the number of web means. .Iaddend.
.Iadd.20. The miniature axial fan of claim 19 wherein the housing
has an inward circular configuration. .Iaddend. .Iadd.21. The
miniature axial fan of claim 20 wherein the circular configuration
encloses the rotor disk. .Iaddend.
Description
BACKGROUND AND SUMMARY OF THE INVENTION
The invention relates to a miniature axial fan particularly of an
axially compact construction, having a central motor driving a
rotor disk with a housing surrounding the rotor disk in which an
interior housing wall on the inflow side is cylindrical and extends
past the axial center of the housing and then this cylinder wall
expands outwardly to the outlet side of the housing to produce an
enlargement of the flow cross-section. The housing has webs
extending inwardly from the outlet side of the housing that carry
the central driving motor with the rotor disk. A number of blades
are mounted on the rotor disk which numbers differs from the number
of webs.
In the case of axial fans of such a small size, there is, in
addition to the often required compactness, the requirement of a
low noise level and of an air output that is sufficient for its
use. Because of the given small outside dimensions that is not easy
to achieve. In the range of these dimensions and below, there is
therefore a struggle involving millimeters. If one parameter, one
dimension is changed by a few millimeters in favor of one
characteristic, this has a considerable effect on other
characteristics and thus on the overall characteristics.
On the basis of the European Patent Application 0100078, an axial
fan is known that is suitable for a rotor disk diameter of below
100 mm.
The invention is therefore based on the objective of developing a
very small, relatively compact axial fan having a rotor disk driven
by a concentric coaxial driving motor in such a way that, in the
case of the small size offered here, it has a relatively good air
output and a low noise level.
The invention is achieved by the means of a miniature axial fan,
particularly of an axially compact construction, having a central
motor driving a rotor disk with a housing surrounding the rotor
disk in which an interior housing wall on the inflow side is
cylindrical and extends past the axial center of the housing and
then this cylinder wall expands outwardly to the outlet side of the
housing to produce an enlargement of the flow cross-section. The
housing has webs extending inwardly from the outlet side of the
housing that carry the central driving motor with the rotor disk. A
number of blades are mounted on the rotor disk which numbers
differs from the number of webs. A rotor disk has a diameter of no
more than 60 mm. The blades are designed in such a way that on the
output side they have a large adjusting angle of 70.degree. to
90.degree. due, to the fact that when viewed in a top view, that is
radial with respect to the axis of rotation onto the blade, the
bend of the blade from the direction of the inlet side is at first
slight and this bend then changes into a bend that becomes more
extensive up to the blade edge on the outlet side.
These and other objects, features, and advantages of the present
invention will become more apparent from the following description
when taken in connection with the accompanying drawings which show,
for the purpose of illustration only, plural embodiments in
accordance with the present invention, and wherein:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view along the Cutting Line I/I of FIG.
2.
FIG. 2 is a top view in the direction of the Arrow II of FIG. 1.
FIGS. 1 and 2 are both shown in twice their real size, thus at a
scale of 2 : 1, and show a fan housing into which a rotor disk with
a coaxial driving motor can be inserted.
FIGS. 3, 3a, 4, 5 show variants of such driving motors according to
the invention also having a rotor disk in twice the real size, in
which case the outer rotors of the driving motor and the rotor disk
hub are developed differently.
FIG. 6 is an embodiment with an additional or alternative fastening
of the plastic rotor disk on the outer rotor can by means of
heat-upsetting. In addition, an electronic commutating system is
provided there on a ring-shaped support under the outer rotor
cap.
FIGS. 7 and 8 are details of the blade dimensioning for the rotor
disk.
DETAILED DESCRIPTION OF THE DRAWINGS
Referring now to the drawings wherein like reference numerals are
used to designate like parts and more particularly to FIG. 1 shows
a bent longitudinal section through the housing 1 of a miniature
fan according to the invention. Concentrically to the rotational
axis 10 is a bearing tube 17 having a plurality of stepped ridge
portions acting as stops for bearings and for positioning of the
stator body.
The bearing tube 17 is unitarily formed with the flange 13 which
has an outer edge 4' to which four radially extending webs 5 are
connected at 90.degree. intervals. The webs 5 extend into the
center area of a square sideof the fan housing tube 4 at an
externally shaped square flange plate 15. The housing tube 4
extends axially along rotational axis 10 with its cylindrical
interior wall surface 3 extending from the inlet plane E to the
outlet plane at flange 13. Radially outside the housing tube 4 are
fastening columns 14 at corners of the square flange plate 15. The
columns also extend from the outlet plane A axially to the inlet
plane E. All these parts bearing tube 17, flange 13, webs 5, tube
4, housing 1, column 14, and flange plate 15 are developed as a
one-piece plastic injection molded part. The fastening columns 14
extend the full axial length of the fan and have a compact
construction to provide an excellent stiffness for the fastening of
the minifan. In addition, by means of this unitary design for
forming the inside and outside flow duct, with only one joint face,
the housing 1 can be created in an inexpensive mold. The fastening
bores 16 of the columns 14 are concentric with axis 10.
The enlarging spaces 18, 19 with the enlarging angle .gamma.,
.delta. at the outlet plane A that extend from the cylindrical part
of the interior wall surface 3 to the outlet plane A, ensure
because of their very small angle .delta. that the housing can be
easily removed from the mold while additionally providing an
increase of the cross-section area of the flow duct at the outlet
plane A, even though the increase is minimal. The cylindrical part
of the interior wall surface 3, for reasons of manufacturing
technology in the case of the injection-molded piece, must have an
incline to aid for in the lifting-out of housing from the mold.
I.e., this cylindrical part is only essentially cylindrical
(compare angle .delta.). The enlarging spaces 18 into the four
corners of the square end plate 15 with the significantly larger
enlarging angle .gamma. are known per se from the German Patent
Text 17 28 338. The enlarging spaces 18 also extend conically (or
in steps) to the outlet plane A from the direction of the
cylindrical part 3 of the flow duct.
The diagonal wall of the enlarging spaces 18 is shown from the
outside in FIG. 2 (compare number 27). Between the fastening
columns 14 and the housing tube 1, continuous bridges 28 are
provided that provide stability to the columns 14 and to the
housing tube 1. On the side of the inlet, the interior wall surface
3 has a rounded off area which in practice, in its real size, has a
bending radius of about 4 to 5 mm.
The real size of FIGS. 1 and 2 is therefore that of a cuboid of
50.times.50.times.25 mm. In the present construction that is shown
in FIG. 1 and 2, this provides for: a combination of an optimal
flow duct, a relatively high stability of the housing structure, an
economical manufactured product, with dimensions of a small size.
To obtain this product, measurements and proportions have
significance. The round columns 14 that are developed with round
holes for the continuous fastening bolts 16 and the thin bridges 28
that continue over the whole axial length of the housing radially
to the thin housing ring 1, make possible for an optimal and simple
molding process.
In FIGS. 3, 4, 5, the bearing tube 17 and the flange 13 are
constructed as shown in FIG. 1. The armature stampings of the
stator are fitted onto the inlet end facing step of the bearing
tube 17, and strike against this step with insulating end plates.
In the interior of the bearing tube 17, a pair of ball bearings 80
and 80b are braced axially by a spring 81 for supporting a shaft 12
that in a torsionally fixed way is connected with the outer rotor
housing 2, or the rotor disk hub 33. FIGS. 3 to 5 are constructed
differently only with respect to the configuration of the outer
rotor cap 2 and the rotor disk hub 33 (FIGS. 3,4) and 50 (FIG. 5).
In all three cases, identical blades 7 can be combined on a hub 22
(FIG. 3), hub 33 (FIG. 4), or on hub 50 (FIG. 5). Also the armature
stampings are identical with the winding of a driving motor 6 as
well as the electronic commutating system 20--located axially and
internally in the flange shell 13.
In the case of axial fans of this small size, it is important, when
using a relatively large driving motor 6, where there is a relative
large ratio of the diameter the rotor disk hub 22, 23, or 50 or the
driving motor diameter--to the outer diameter of the envelope of
the blade ends at the interior walls 3, to make the radial
dimension of the blade relatively large. In other words, it is
desirable to construct the driving motor and hub so as to extend
for a small portion of the inner diameter of the interior of flow
wall 3. The pump air flow duct is defined as the area formed by the
hub and the outer rotor interiorly and the flow wall 3 exteriorly.
The object of FIGS. 3, 4, 5 is to provide conditions that are
favorable to achieve a certain output requirement and a secure
fastening of the rotor disk blades 7 at the plastic hub 22 and 50,
as well as of the fan wheel on the outer rotor and to nevertheless
make available a sufficient air output.
In FIG. 3, a plastic-bound magnet is used (or a ceramic magnet, but
always still a magnet) of a relatively large thickness, over which
a relatively thin bowl-shaped cap 33 of low retentivity is pulled.
The rotor disk hub 21, with its cylindrical exterior part 22,
completely reaches around the cap 33, whereby good anchoring is
achieved by the fact that at the open end 24 of the bowl, the
plastic is thickened inward to partially enclose the cap 30, i.e.,
by means of the plastic hub 21 with its exterior part and thickened
end. A form-locking holding of the outer rotor is achieved by means
of the fact that the injection molding takes place around the
bowl-shaped cap 33 , whereby the exterior part 22 with the radial
wall 21 as a whole is combined into bowl-shaped hub and with the
blades 7 into a rotor disk 2 that in a known manner is developed in
one part as an injection-molded part.
FIG. 3 shows a further independently important economically
advantageous method and structure to fix the rotor 2 on the shaft
12 by mere plastic injection molding. The soft-iron cap 33 with its
inner axially bent collarlike rim 133 there is completely embedded
in the plastic means. The internal surface 134 of said collar like
rim 133 is separated by a distance of about 0.5 to about 2 mm from
the shaft 12, and preferably the distance is 0.6 mm. This distance
or gap 137 is filled with plastic and the collar like rim 133 is
partly perforated, so that the plastic part 135 surrounds and
penetrates the rim or collar like rim 133. The gap is as small as
possible so that plastic material, when injected, penetrates the
gap. Because of heat problems the gap should be no larger than 1 to
2 mm. Said cylindrical collar surrounding said shaft is fixed with
the rotor in any well known way.
FIG. 4 shows a known, more costly method of locating the blades 7
about the shaft 12 where a separate additional metal piece 139 is
located between the shaft and the collar is necessary.
The method of FIG. 3 is important, independently of the type of fan
or structure of the rotor housing.
In FIG. 3, the internal rim of the rotor-holding reinforcement cap
element 33 is punched and bent in one step with the whole caplike
element 33.
FIG. 4 shows a cylindrical part 25 of a rotor disk hub 26 that only
projects out over a relatively small part, about one fourth of the
axial lengths of the outer rotor of the driving motor. The
bowl-shaped cap element 33 of the outer rotor, that is of low
retentivity, is reduced in its diameter in steps so that a
cylindrical outer surface makes possible a press fit for the
plastic hub 25, 26, in which case its outside diameter corresponds
approximately to the outside diameter of the rotor bowl cap
element. In this way, with otherwise identical engine dimensions, a
slightly larger cross-section is obtained by the elimination of the
cylindrical exterior wall 22 o: the plastic hub 21. Naturally, in
the case of FIG. 4, the plastic hub with theradial front surface 26
and the cylindrical edge part 25 that is developed as a ring collar
are injection-molded in one piece with the blades 7. In this case,
this important expansion of the flow cross-section, i.e., reduction
of the driving motor in its diameter including the rotor disk hub,
takes place by such a reduced diameter.
Should the mounting of this rotor disk on the outer rotor not be
good enough, it may, as shown in FIG. 6, be held in addition or as
an alternative in the end of the rotor cap element 70 by means of
journals 72 that are upset from the hub by heating. This would make
it possible that the cylindrical end projection 25 can be
eliminated. In that case, a cone-type tapering could be provided in
the direction of the inlet plane E. The reason for this type of
cone-type tapering of the rotor disk hub in the direction of the
inlet plane E is to make possible an additional improvement of the
flow behavior, particularly if, on the outside, the limiting
housing wall were to extend at first cylindrically from the flow-in
side, as in known on the basis of EP-0100 078-A1 (EU-456).
In principle, it can be stated that this hot upsetting of the rotor
disk hub in the front side of the outer rotor cap, as shown in FIG.
6, is useful as an additional measure or as an alternative. Thus a
glueing-together or riveting-together may also take place so that,
in the area of the reduced diameter, as shown in FIG. 6, by means
of a conical outer contour of the rotor disk hub, or one that
tapers in the direction of the inlet plane E as a whole, clearance
73 is created. That is also shown on the right-hand side of FIG. 6
where it is shown clearly that the ring part was left out.
If the rotor disk is made of a fiber-glass-reinforced plastic, this
type of construction can be afforded. The blades will nevertheless
adhere with the required stiffness to the disk-shaped hub 56. If
the rotor disk is a metallic punched bent part, it is advantageous
to rivet tee disk-shaped hub together with the rotor of the driving
motor.
FIG. 5 shows an additional variant, where a radially deeper
tapering step 65 is obtained to provide, a further enlargement of
the inlet flow cross-section area.
By means of a more extensive reduction of the outer diameter of the
housing 50 to the cylindrical step 52, of a diameter of 50 to 80%
of the housing 50 because of the relatively small ring part 53 of
the hub, there is still a sufficient amount of cross-section left
to achieve a perfect press fit not only on the outer surface 54 of
the housing step 52, but in addition, because there is sufficient
cross-section, the outer contour of the plastic hub 2 with its
overlapping ring part 53 can be constructed in such a way that it
has a conical surface 65 that tapers in the direction of the inflow
plane E, which again is favorable with respect to the flow,
somewhat similar to that shown above in connection with FIG. 6. If
the surface 65 extends axially at least over 1/3 of the flow duct
length, this tapering is quite effective. Particularly by means of
the concept of FIG. 5 , this minimal length can be achieved in a
mass-produced product without any problems. In the case of this
embodiment, less demands are made on the plastic that carries the
one-piece rotor disk 2 with the blades 7. Also having the ring part
53 with the radial bottom wall 55 plastic, may possibly be less
expensive. In the case of FIG. 5, a rare-earth alloy, such as
samarium cobalt, is used for the rotor magnet 57. It is known that
these types of magnets require a much smaller volume so that the
permanent magnet in a tube form may also be much thinner its radial
thickness which, again in the case of the same air gap (the same
magnetic conditions are a prerequisite), results in a further
reduction of the outside diameter of the can 50. Thus, the small
outside diameter of the driving rotor (in the case of the
samarium-cobalt permanent magnet solution used here) and the
radially extensive reduction of the step 52 (i.e., in the case of a
ratio of the diameter of the step 52 to the diameter of the
cylindrical part 50 of the outer rotor housing of 0.5 to 0.8)
results in an effective conical tapering of the engine rotor disk
hub in the direction of the inlet plane E. Again, in the case of
FIG. 5, the same rotor may be provided as in FIGS. 3 or 4 so that
therefore the same air gap diameter applies. In the case of FIG. 5,
the whole radius natural wall thickness of the rotor bundle with
the parts 50 and 57 is about 1 to 2 mm, and in the case of FIG. 3,
it is about 3 to 4 mm which signifies a reduction of diameter of
about 4 mm which is very important in the case of this small size
(hub diameter about 30 mm) because the flow cross-section is
significantly improved by the enlargement and design. This concept
of FIG. 5 is basically advantageous for miniature fans with a
central motor, particularly with outside rotors, independently of
the housing. It is also advantageous for miniature, so-called
"motor rotor disks" (i.e. motors in which the rotor disk is placed
on the motor). It is not only for use with rare-earth rotor magnets
(with or without cobalt), but very effective when they are used.
Weaker magnets signify a slightly larger "hub" diameter.
In FIG. 6, on the left-hand side, a slightly different variant of a
fan according to the invention is provided, in which a reduction of
the outside diameter of the motor hub is visible.
FIG. 6 shows an injection-molded plastic fan wheel 2 having a hub
portion 19a which carries the evenly distributed blades 7 on its
periphery. It is pressed over the hub part 70 of the outside rotor
housing 22 that is reduced in its diameter and is fastened in any
secure manner. The outside diameter of the plastic hub 21
corresponds largely to the outside diameter of the rotor housing 22
near its open end.
The advantage of the plastic fan wheel is the fact that it results
in an altogether cost-effective axial fan. It is also
understandable that the outside diameter of the hub 21 is still
smaller than would be the case if this hub were to completely reach
over the outside rotor of the driving brushless direct-current
motor. Therefore, the rotor constructed according to FIG. 6 with
the fan wheel that is placed on it, is advantageously used in very
small axial fans. The reason is that here, in the range of a rotor
disk diameter of 30 to 60 mm with a coaxial "hub" motor, a minimal
reduction of the rotor disk hub diameter is quite advantageous for
the flow behavior (air volume/time and noise).
Although it is shown in FIG. 6 that the central fastening part 32
is the bearing tube, it should be clear that for many usages the
central fastening part could also consist of only the interior side
of the iron core 58 of the stator. Thus, the stator iron could be
used as a fastening either for the ball bearings 48, 48' as shown
in FIG. 5 or for slide bearings 49 in the case of certain usages of
the brushless direct-current motor. The printed circuit board 20,
in this case, would be fastened by means of pins at the appropriate
point of the stator.
A further improvement of the structure consists of equipping the
motor of FIG. 6 with the fan housing 37, the central fastening part
32, the flange 30 as well as the webs 5 out of a single cast
plastic part.
Thus, an interior motor structure is shown for a brushless
direct-current motor having an electronic driving system and a
revolutions/min. control circuit that, on the inside of the motor,
is fastened on a master board in such a way that it is possible to
obtain in steps, a smaller diameter at the closed end of the hub of
the outside rotor than at the open end of the outside rotor. This
diameter that becomes smaller in steps makes it possible to use
this type of motor for axial fans having a larger cross-section on
the air inlet side of the fan, particularly in the case of a fan
with smaller dimensions, as well as for usages where it is
important that larger amounts of air be supplied at a higher
pressure.
FIG. 7 is a partial view of the rotor disk hub 2, particularly
according to FIG. 3. The blades 7 are arranged in a non-continuous
distributed way at the circumference of the rotor disk hub 2. The
clearance 75 (in this case about 3 mm) is varied in order to reduce
noise. The flow direction is indicated by the arrow 74. The inlet
edges 71 of the blades 7 are staggered by a first axial distance 61
from the inlet Plane E in the direction of an Arrow 74 that
indicates the flow direction. In the embodiment according to FIG.
3, for example, this distance 61 is 3 mm. The inlet edge is
developed with a radius of about 0.6 mm. In its demonstration last
third, the blade 7 is tapered and ends at the outlet edge 72 with a
thickness of 0.4 mm. The outlet edge 72 is set back by a second
distance 62 in the opposite direction of the Arrow 74 from the
inner web edge 59 of the webs 5, namely preferably 4 mm (compare
FIG. 3). The axial dimension 63 of the rotor disk 2 (according to
FIG. 3) is about 20 mm. The inlet angle .epsilon. at the inflow
side that is formed by the tangent line at the radial exterior side
of the blade edge 71 and the inflow plane E, is located in the
range of 25.degree. to 45.degree. . The adjusting angle .alpha. at
the outflow side, formed by the tangent line at the radial exterior
side of the blade edge 72 and the outflow side A, is 70.degree. to
90.degree., preferably 80.degree..
FIG. 8 shows the blade 7 as a part that is developed in a plane
(and can, for example, be extruded or drawn out in this way). The
blade 7 is developed on both sides of an axis 76 that has an angle
of slope of about 45.degree. with respect to the blade root, with
different radiuses R 1 and R 2. The diameters of the two bending
cylinders on both sides around the axis 76 are for 2 R 1=120 mm and
2 R 2=30 mm. In the case of a radial top view of the blade 7, the
bend R 1 of the blade from the direction of the inlet edge 71 is at
first slight and then changes into a more extensive bend R 2.
While we have shown and described only plural embodiments in
accordance with the present invention, it is understood that the
same is not limited thereto but is susceptible to numerous changes
and modifications as known to one having ordinary skill in the art,
and we therefore do not wish to be limited to the details shown and
described herein, but intend to cover all such modifications as are
encompassed by the scope of the appended claims.
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