USOO6296446B1
(12) United States Patent (10) Patent No.: US 6,296,446 B1
Ishijima et al. (45) Date of Patent: Oct. 2, 2001
(54) AXAL BLOWER 4,128,363 * 12/1978 Fujikake et al. ................. 416/236 A
5,169,290 12/1992 Chou ................................ 416/236 R
(75) Inventors: Mitsuyoshi Ishijima; Tetsuya 5,193.983 * 3/1993 Shyu - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 416/236 R
Koshitani; Satoshi Shimizu, all of Fuji
(JP) * cited by examiner
(73) Assignee: Toshiba Carrier Corporation, Tokyo Primary Examiner Edward K. Look
(JP) ASSistant Examiner-Richard Woo
(74) Attorney, Agent, or Firm-Oblon, Spivak, McClelland,
(*) Notice: Subject to any disclaimer, the term of this Maier & Neustadt, P.C.
patent is extended or adjusted under 35
U.S.C. 154(b) by 0 days. (57) ABSTRACT
An axial blower includes a cylindrical hub, a driving device
(21) Appl. No.: 09/409,072 for rotating the cylindrical hub through a rotational shaft, a
(22) Filed: Sep. 30, 1999 plurality of Vanes arranged to an Outer peripheral Surface of
the cylindrical hub in a circumferential direction thereof, and
(30) Foreign Application Priority Data a plurality of Stream-line ribs each having a stream-line
Sep. 30, 1998 (JP) ................................................. 10-2791.16
shape and provided at a leading edge portion of a negative
preSSure Surface-side of each of the Vanes in a range from an
(51) Int. Cl." .................................................. F04D 29/38 end portion of the leading edge portion towards a trailing
(52) U.S. Cl. .................................. 416/236 A, 416/236 R; edge portion of the Vane. The Stream-line ribs are formed
416/DIG. 2; 416/238 integrally Such that an Outer Surface of a croSS Section of
(58) Field of Search ............................ 416/236 R, 236 A, each Stream-line rib along a rotational direction of the axial
416/238, 223 R, 228, 243, DIG. 2, DIG. 5 blower forms a circular arc and a radius of a circular arc
curve of the outer Surface at a vane leading edge Side is
(56) References Cited larger than a radius of a circular arc curve at a vane inner
Surface Side.
U.S. PATENT DOCUMENTS
2,912,159 * 11/1959 Ganger et al. ................... 416/236 A 6 Claims, 6 Drawing Sheets
3d
3e
U.S. Patent Oct. 2, 2001 Sheet 1 of 6 US 6,296,446 B1
U.S. Patent Oct. 2, 2001 Sheet 2 of 6 US 6,296,446 B1
14b. p 140
FIG. 3
U.S. Patent Oct. 2, 2001 Sheet 3 of 6 US 6,296,446 B1
3d
8/L 10/L 12/L 14/L 16/L
RATO
(LENGTH L OF NEGATIVE PRESSURE-SIDE
LEADING EDGE OF WANE TO D STANCE
BETWEEN ADJACENT RIBS)
F. G. 6
U.S. Patent Oct. 2, 2001 Sheet 4 of 6 US 6,296,446 B1
Zb
Zd
F. G. 8
U.S. Patent Oct. 2, 2001 Sheet S of 6 US 6,296,446 B1
h
h
Yb ht
YG
F. G. 9
F. G. 10
PRIOR ART
U.S. Patent Oct. 2, 2001 Sheet 6 of 6 US 6,296,446 B1
B
3b
A 3C
3C 3d
F. G. 11
PRIOR ART
F. G. 12
PRIOR ART
US 6,296,446 B1
1 2
AXAL BLOWER The plurality of Stream-line ribs are arranged with equal
distance from each other and the distance between the
BACKGROUND OF THE INVENTION adjacent Stream-line ribs is Set at L/12 with respect to a
The present invention relates to an axial blower used for length L of the negative pressure Surface-side leading edge
a blower of an outdoor unit of an air conditioner or the like. portion along a radial direction of the axial blower. The
One example of a conventional axial blower of this type Stream-line ribs are formed integrally Such that an outer
is shown in, for example, FIG. 10. This axial blower 1 is Surface of a croSS Section of each rib along the rotational
direction of the axial blower forms a circular arc and a radius
provided with a plurality of vanes 3 formed integrally of a circular arc curve of the outer Surface at a vane leading
around a central hub 2 equidistantly in the circumferential edge Side is larger than a radius of a circular arc curve at a
direction thereof. Vane inner Surface Side.
With reference to FIGS. 10-12, the cross-sectional shape The Stream-line ribs have lengths k at a vane outer
of each vane 3 in the circumferential direction A-B at a periphery Side along the rotational direction of the air blower
portion having a radially arbitrary distance D from the center are Set equal to one another. The lengths k of the Stream-line
O of the hub 2 is formed into a thick stream-line shape 3d 15
ribs at the Vane outer periphery Side along the rotational
from the negative preSSure Surface-side leading edge portion direction of the axial blower are set to satisfy a relation of
3a of the vane 3 to a vane Surface 3c as shown in FIG. 11. k:CL=1:9, where CL is a chord length of the vane outer
The thick shape 3d advantageously allows an air flow F periphery.
flowing from the negative pressure Surface-Side leading edge A height of the cross-section of each of the ribs along a
portion 3a of the vane 3 to travel along the positive and thickness direction of each of the Vanes is changed to be
negative preSSure Sides of the Vane Surface 3C as indicated by made gradually larger from the hub side towards the Vane
arrows shown in FIG. 12, prevents the air flow F from outer periphery direction in a manner reverse to that a
Separating from the Vane Surface 3c and makes Small a thickness of a croSS Section of the Vane leading edge portion
trailing Vortex Vf formed in the back of a vane trailing edge is made gradually Smaller from the hub side towards the
portion 3b thereby to reduce a blowing sound. direction of the Vane outer periphery.
When the conventional axial blower 1 as mentioned
25 The plurality of stream-line ribs include a rib closest to the
Vane outer peripheral Side having a heighth, and a rib closest
above is incorporated, as a blower, into the outdoor unit of to the hub side of a stream-line rib closest to the vane outer
an air conditioner to increase the number of revolution of the periphery Side having a heighth, the heights being set So as
blower per unit time (to be simply referred to as “the number to Satisfy an equation h-2h.
of revolution' hereinafter) and to increase the quantity of According to the present invention of the Structures
blast, following disadvantages occur. That is, Static pressure mentioned above, in the main aspect, the plural Stream-line
in the outdoor unit rises, the inflow angle of the air flow F ribs at the negative pressure Surface-side leading edge
with respect to the negative pressure Surface-side leading portion of each vane accelerate the transition of a laminar
edge portion 3a of each Vane 3 varies and the Separation of flow to a turbulent flow above a vane surface boundary layer
the air flow tends to occur on the Vane Surface 3c, thus 35 of each vane. The flow above a turbulent flow boundary
increasing the blowing Sound. layer is leSS Separated than that above the laminar boundary
Further, it is easily be understood that the term “negative layer. Thus, it is possible to both enhance blast performance
preSSure Side' used herein means an air-Sucking Side and the and reduce blowing noise.
term “positive pressure Side' used herein means an air In the other aspects of the embodiment, each of the
blowing side with respect to the vanes of the axial blower. 40 Stream-line ribs is arranged Such that a central axis of the rib
SUMMARY OF THE INVENTION along a rotation direction of the blower passes a point of
interSection of a circular arc about a center of a vane outer
An object of the present invention is to Substantially periphery leading edge-side circular arc portion and the Vane
eliminate defects or drawbacks encountered in the prior art leading edge and is parallel to a tangent of the circular arc.
mentioned above and to provide an inexpensive axial blower 45 Accordingly, when an air-flow flowing from the negative
capable of Suppressing the increase of blowing Sound due to preSSure Surface-side leading edge of each Vane passes the
the Separation of a flow generated on the negative pressure Stream-line ribs, the air-flow forms longitudinal Vortex rows
Surface Side of the Vane and has excellent formability. thereby to make the transition of a layer above the vane
This and other objects can be achieved according to the Surface to a turbulent boundary layer. This action can make
present invention by providing an axial blower comprising: 50 narrow the widths of the trailing vortexes which cause the
a cylindrical hub; blowing Sound and can reduce the blowing Sound.
a driving means for rotating the hub through a rotational The plural Stream-line ribs are arranged equidistantly and
shaft; the distance between the stream-line ribs is set at L/12 with
a plurality of Vanes arranged to an outer peripheral Surface respect to a length L of the negative pressure Surface-side
of the hub in a circumferential direction thereof, and 55 leading edge portion along a radial direction of the blower.
a plurality of ribs, each having a Stream-line shape, Accordingly, even if Static pressure within the blower
provided at a leading edge portion of a negative pres increases and the inflow angle of the air-flow at the negative
Sure Surface-Side of each of the Vanes in a range from preSSure Surface-side leading edge portion of each Vane is
an end portion of the leading edge portion towards a changed, the blowing Sound can be reduced.
trailing edge portion of the Vane. 60 Furthermore, if the radius of a circular arc curve thereof
In a preferred embodiment, each of the Stream-line ribs at a vane leading edge Side becomes larger than that of a
has a central axis along a blower rotational direction, the circular arc curve at a vane inner Surface Side on the circular
central axis passing a point of interSection of a circular arc arc croSS Section of each Stream-line rib along the rotational
having a center point of a circular arc portion on a vane outer direction of the blower, longitudinal vertexes generated
periphery leading edge-side and the Vane leading edge 65 when air flows pass through the Stream-line ribs can be
portion and being Substantially in parallel to a tangent of the generated Stably and the blowing Sound reduction effect can
circular arc. be further improved.
US 6,296,446 B1
3 4
Still furthermore, Since, the lengths k of the Stream-line FIG. 2 is a perspective view of an axial blower 11 in a first
ribs at the Vane outer periphery Side along the rotation embodiment according to the present invention as viewed
direction of the air blower are set to satisfy k:CL=1:9 where from a negative pressure Surface Side.
CL is a chord length of the Vane Outer periphery, the blowing AS mentioned hereinbefore, in the described embodiment,
Sound reduction effect can be maximized. it will be also easily understood that the term “negative
Still furthermore, Since the thickness of the Vane leading preSSure Side' used herein means an air-Sucking Side and the
edge portion is changed So as to be gradually Smaller from term “positive pressure Side' used herein means an air
the hub side toward the vane outer periphery side, if the blowing side with respect to the vanes of the axial blower.
height h of each Stream-line rib is changed So as to be FIG. 1 is a partially omitted front view of the axial blower
gradually larger from the hub side towards the Vane outer 11 of FIG. 2 at the negative pressure surface side. The axial
peripheral direction oppositely from the change of the Vane blower 11 is provided with a central cylindrical hub 12 and
thickness, and the heighth, of the Stream-line rib at the Vane a plurality of vanes 13 formed integrally with the hub 12
outer periphery Side and the height ha of the Stream-line rib equidistantly on the Outer peripheral Surface in the circum
at the hub side are formed to satisfy the relationship of ferential direction thereof. The central hub 12 is coupled
h=2h, then the thickness of the croSS Section including the 15 with a rotation shaft 10 of a driving motor M, such as electric
thickness of the negative pressure Surface-side leading edge motor, So as to be rotated thereby.
portion becomes equal in any points. Accordingly, it is AS also shown in FIG. 1, the axial blower 11 has a
possible to shorten a cooling time and reduce the shrinkage plurality of ribs 14, each having a stream-line shape,
of the vane while integrally forming the axial blower with a Smoothly ranging from a leading edge fillet 13c towards a
resin or like. trailing edge portion 13d on the negative preSSure Surface
The nature and further characteristic features of the Side leading edge portion 13b of the leading edge portion
13a of each of the vanes 13. The stream-line ribs 14 are
present invention will be made more clear from the follow aligned to have a predetermined distance from each other in
ing description made with reference to the accompanying the radial direction of the axial blower 11.
drawings.
25 The stream-line ribs 14 are arranged in the following
BRIEF DESCRIPTION OF THE DRAWINGS manner. That is, providing that a center of the leading edge
In the accompanying drawings: Side circular arc portion 13e on the outer periphery of the
FIG. 1 is a front view, partially removed, of an axial vane is referred to as “P”, the ribs 14 pass points of
blower according to one embodiment of the present inven interSections Sn of a plurality of arcs C. n of concentric
tion as viewed from a vane negative pressure Surface Side of circles of different diameters with the center P being the
an axial blower shown in FIG. 2, mentioned latter; center of the circles and the leading edge end of the leading
FIG. 2 is a perspective view of the axial blower as viewed edge fillet 13c. The central axes of the respective stream-line
from the negative pressure Surface side of the vane, ribs 14 along the rotational direction of the axial blower are
parallel to the tangents of the arcs C. n, respectively.
FIG.3 is a cross-sectional view of a stream-line rib shown
in FIG. 2 taken along the line Xa-Xb; 35 Furthermore, as shown in FIG. 1, the plural stream-line
ribs 14 are arranged equidistantly in the radial direction of
FIG. 4 is a partial front view of the axial blower for the blower and the interval of the ribs 14 is set at L/12
describing the function of the embodiment shown in FIG. 1; relative to the length L of the negative pressure Surface-side
FIG. 5 is a cross-sectional view of a vane shown in FIG. leading edge portion 13b in the radial direction of the
4 in a circumferential direction; 40 blower.
FIG. 6 is a graph showing a relative relationship between FIG. 3 shows the outer surface (or upper surface in FIG.
a ratio of a length L of the negative pressure-side leading 3) of the cross-section of the cut portion when each stream
edge portion of the Vane to a distance between adjacent line rib 14, which is cut in the direction of the line Xa-Xb
Stream-line ribs and showing a blowing noise reduction shown in FIG. 1 along the axial direction of the ribs 14 forms
effect of the embodiment shown in FIG.1; 45 a stream-line, arc-shaped croSS Section. The Stream-line rib
FIG. 7 is a partial front view showing a length k of the 14 is formed Such that the radius R1 of the arc curve 14a at
Stream-line rib at the Vane outer periphery Side and a length the vane leading edge portion (13a) side (or Xa side in FIGS.
CL of the outer periphery of the vane; 1 and 3) end portion is larger than the radius R2 of an arc
FIG. 8 is a cross-sectional view of the negative pressure curve 14b at the vane trailing edge portion (13d) side (or Xb
Surface-side leading edge portion of the Vane in the radial 50 side in FIGS. 1 and 3) end portion.
direction of the axial blower in one embodiment according FIG. 4 is a partial front view showing the function of the
to the present invention; axial blower 11 constituted as stated above. FIG. 5 is a
FIG. 9 is a cross-sectional view of the stream-line rib cross-sectional view of the axial blower 11 in the circum
taken along line the line Ya-Yb of FIG. 7; ferential direction of each of the vanes 13. As shown in
FIG. 10 is a front view of a conventional axial blower as 55 FIGS. 4 and 5, when an air-flow F travels from the leading
Viewed from a vane negative preSSure Surface Side; edge fillet 13a of the vane 13 towards the vane inner surface
FIG. 11 is a cross-sectional view of the vane when the (13f) side as indicated by a large arrow and passes the plural
vane shown in FIG. 10 is circumferentially cut at an arbi stream-line ribs 14, a plurality of air-flows F form longitu
trary radius R; and dinal vertex rows 15, respectively, as indicated by small
FIG. 12 is a cross-sectional view of the vane showing air 60 arrows and transferred towards a turbulent boundary layer
flows of the conventional axial blower shown in FIG. 10. above the vane inner Surface 13f. The turbulent boundary
layer can SuppreSS the Separation of flows more than in a
DESCRIPTION OF THE PREFERRED case of a laminar boundary layer and makes narrow the
EMBODIMENTS widths of the trailing Vortexes which cause blowing Sound,
One preferred embodiment according to the present 65 thus reducing blowing Sound.
invention will be described hereunder with reference to FIG. 6 shows the noise reduction effect in the case where
FIGS. 1 through 9. a plurality of Stream-line ribs 14 are arranged equidistantly
US 6,296,446 B1
S 6
along the radial direction of the blower and the distance negative pressure Surface-side of each of the Vanes in a
between the ribs 14 is set at L/1 with respect to the length range from an end portion of the leading edge portion
L of the negative pressure Surface-Side leading edge portion towards a trailing edge portion of the Vane, Said Stream
13.b in the radial direction of the blower. That is, when the line ribs being formed integrally Such that an outer
axial blower 11 thus formed is incorporated into, for Surface of a croSS Section of each Stream-line rib along
example, the outdoor unit of an air conditioner, the Static a rotational direction of the axial blower forms a
preSSure within the outdoor unit increases. Accordingly, circular arc and a radius of a circular arc curve of Said
even if the inflow angle Y (see FIG. 4) of the air-flow at the Outer Surface at a vane leading edge Side is larger than
negative pressure Surface Side leading edge portion 13b in a radius of a circular arc curve at a vane inner Surface
the radial direction of the Vane be changed, the blowing Side.
Sound can be reduced. 2. An axial blower according to claim 1, wherein each of
As shown in FIG. 7, the stream-line ribs 14 are formed so Said Stream-line ribs has a central axis along the rotational
that the lengths k of the ribs 14 at the vane outer periphery direction of the axial blower, Said central axis passing a point
(13a) side in the rotational direction of the blower are equal of interSection of a circular arc having a center point of a
to one another and the ratio of k to CL is set at k:CL=1:9 15 circular arc portion on a vane outer periphery leading
where CL is the chord length of a vane outer periphery 13.g. edge-side and the leading edge portion and being Substan
This can further reduce the blowing noise. tially in parallel to a tangent of the circular arc.
FIG. 8 is a cross-sectional view of the negative pressure 3. An axial blower according to claim 1, wherein Said
Surface-side leading edge portion 13a of each Vane 13 in the plurality of Stream-line ribs are arranged with equal distance
radial direction of the blower. The thickness ho of the cross from each other and the distance between the adjacent
Section is changed So as to become gradually Smaller from Stream-line ribs is Set at L/12 with respect to a length L of
a hub side Za towards to a vane outer periphery (13g) side the leading edge portion along a radial direction of the axial
Zb. blower.
4. An axial blower comprising:
Meanwhile, the height h of each stream-line rib 14 is a cylindrical hub;
changed So as to be gradually larger from a hub side Ya 25
towards a vane outer periphery (13g) side Yb as shown in driving means for rotating the cylindrical hub through a
FIG. 9. The heighth of the stream-line rib at the vane outer rotational Shaft;
periphery (13g) side and the height h of the stream-line rib a plurality of Vanes arranged to an outer peripheral Surface
14 at the hub side are formed to satisfy the relationship of of the cylindrical hub in a circumferential direction
h=2h. In other words, the direction in which the heighth thereof; and
of the Stream-line rib 14 increases is exactly opposite to that a plurality of Stream-line ribs each having a stream-line
in which the thickness of the negative preSSure Surface-side shape and provided at a leading edge portion of a
leading edge portion 13a increases. The thickness h, of the negative pressure Surface-side of each of the Vanes in a
cross Section including the thickness ho of the negative range from an end portion of the leading edge portion
pressure Surface-side leading edge portion 13a, and 35 towards a trailing edge portion of the Vane, Said Stream
therefore, becomes equal in any points. As a result, it is line ribs having lengths k at a vane outer periphery Side
possible to shorten a time for cooling the integrally formed along a rotational direction of the axial blower which
axial blower 11 and to reduce the shrinkage thereof while are Set equal to one another So as to Satisfy k:CL=1:9,
forming the blower 11 with resin and the like. where CL is a chord length of the Vane outer periphery.
AS described hereinbefore, according to the preferred 40
5. An axial blower comprising:
embodiment of the present invention, a plurality of Stream a cylindrical hub;
line ribs Smoothly ranging from the negative pressure driving means for rotating the cylindrical hub through a
Surface-side leading edge end of each of the Vanes are rotational Shaft;
provided at the negative pressure Surface-side leading edge a plurality of Vanes arranged to an outer peripheral Surface
portion of the Vane and the ribs are arranged Such that the of the cylindrical hub in a circumferential direction
central axes thereof pass the points of interSection of the 45
thereof; and
circular arcs about the center of the circular arc portion at the
Vane outer periphery leading edge Side and the leading edge a plurality of Stream-line ribs each having a stream-line
end and are parallel to the tangents of the circular arcs, shape and provided at a leading edge portion of a
respectively. Thus, it becomes possible to generate longitu negative pressure Surface-side of each of the Vanes in a
dinal vertex rows of air-flows above the Vane negative 50 range from an end portion of the leading edge portion
preSSure Surface and to reduce the blowing Sound. It is also towards a trailing edge portion of the Vane,
possible to improve the formability of the vane due to the wherein a height of the cross-section of each of the
Stream-line shape of each rib. Stream-line ribs along a thickness direction of each of
It is to be noted that the present invention is not limited the Vanes is changed to be made gradually larger from
to the described embodiment and many other changes and 55 a cylindrical hub side towards a vane Outer peripheral
modifications may be made without departing from the direction in a manner reverse to that a thickness of a
Scopes of the appended claims. croSS Section of the leading edge portion is made
What is claimed is: gradually smaller from the cylindrical hub side towards
1. An axial blower comprising: the Vane outer periphery direction.
a cylindrical hub; 60
6. An axial blower according to claim 5, wherein Said
driving means for rotating the cylindrical hub through a plurality of Streamline ribs include a stream-line rib closest
to a vane Outer peripheral Side having a height h and a
rotational Shaft; stream-line rib closest to the cylindrical hub side of a
a plurality of Vanes arranged to an outer peripheral Surface Stream-line rib closest to the Vane Outer periphery Side
of the cylindrical hub in a circumferential direction having a heighth, Said heights being Set So as to Satisfy an
thereof; and 65 equation h =2h).
a plurality of Stream-line ribs each having a stream-line
shape and provided at a leading edge portion of a
