FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
MULTI-BLADE CENTRIFUGAL AIR-SENDING DEVICE;
MITSUBISHI ELECTRIC CORPORATION, A CORPORATION ORGANISED AND
EXISTING UNDER THE LAWS OF JAPAN, WHOSE ADDRESS IS 7-3, MARUNOUCHI
2-CHOME, CHIYODA-KU, TOKYO 100-8310, JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION
AND THE MANNER IN WHICH IT IS TO BE PERFORMED.
2
DESCRIPTION
Title of Invention
MULTI-BLADE CENTRIFUGAL AIR-SENDING DEVICE
5 Technical Field
[0001]
The present disclosure relates to a multi-blade centrifugal air-sending device
including an impeller.
Background Art
10 [0002]
A multi-blade centrifugal air-sending device includes an impeller and a scroll
casing having a spiral shape and housing the impeller. The impeller is constituted by a
back plate, a rim having an annular shape and facing the back plate, and a plurality of
blades provided between the back plate and the rim. The impeller sucks air from the
15 side of the rim by rotating and causes the air to flow out to an air passage in the inside
of the scroll casing through a gap between blades. The airflow is pressurized in the air
passage in the inside of the scroll casing and blown out through a discharge port. As a
means for increasing the air volume in the multi-blade centrifugal air-sending device,
there is a method of increasing the number of the blades. When the number of the
20 blades is increased to increase the air volume, however, noise is increased due to the
increase in the number of the blades. Thus, there is a device (refer to, for example,
Patent Literature 1) in which a forward blade is provided on the outer peripheral side of
a blade and a rearward blade is provided on the inner peripheral side of the blade to
thereby increase the suction air volume with the rearward blade without increasing the
25 number of blades. In the multi-blade centrifugal air-sending device disclosed in Patent
Literature 1, the rearward blade provided on the inner peripheral side of the blade is
configured to be disposed and exposed on the inner side of the inner peripheral end of
a rim, and air is taken in by the exposed rearward blade. An impeller in the multi-blade
centrifugal air-sending device in Patent Literature 1 is formed with a resin material by
30 injection molding.
3
Citation List
Patent Literature
[0003]
Patent Literature 1: Japanese Unexamined Patent Application Publication No.
5 2012-36885
Summary of Invention
Technical Problem
[0004]
When an impeller is formed with a resin material by injection molding as in Patent
10 Literature 1, however, the wall thickness of a blade is larger on the side of a back plate
than on the side of a rim generally due to the moldability of the impeller, and a gap
formed between blades is narrower on the side of the back plate than on the side of the
rim in the impeller. Therefore, although the rearward blade is exposed from the inner
peripheral end of the rim in the multi-blade centrifugal air-sending device in Patent
15 Literature 1, it may be impossible on the side of the back plate to sufficiently take air
that has reached the vicinity of the rearward blade into the gap between the blades and
may be impossible on the side of the back plate in the impeller to obtain an effect of
increasing the suction air volume.
[0005]
20 The present disclosure has been made to solve the aforementioned problem, and
an object of the present disclosure is to provide a multi-blade centrifugal air-sending
device capable of increasing the suction air volume on the side of a back plate in an
impeller, compared with a multi-blade centrifugal air-sending device constituted by a
resin material as in the related art.
25 Solution to Problem
[0006]
A multi-blade centrifugal air-sending device according to the present disclosure
includes an impeller including a back plate having a disk shape, a plurality of blades
arranged at a peripheral portion of the back plate in a circumferential direction, and a
30 rim having an annular shape and disposed to face the back plate, the rim fixing the
4
plurality of blades; and a scroll casing having a spiral shape and housing the impeller,
the scroll casing being configured such that air is introduced from the side of the rim and
blown out to the outer peripheral side. The impeller is constituted by a metal. Each of
the blades has a wall thickness constant from the side of the back plate to the side of
5 the rim and extends toward the inner side further than an inner peripheral end of the
rim.
Advantageous Effects of Invention
[0007]
According to the present disclosure, since the impeller is constituted by a metal,
10 and the wall thickness of each of the blades is constant from the side of the rim to the
side of the back plate, a gap between blades similar to that on the side of the rim in the
impeller can be ensured also on the side of the back plate in the impeller at a portion of
each of the blades extending toward the inner side further than the inner peripheral end
of the rim. Therefore, compared with a multi-blade centrifugal air-sending device
15 constituted by a resin material as in the related art, the suction air volume can be
increased also on the side of the back plate in the impeller.
Brief Description of Drawings
[0008]
[Fig. 1] Fig. 1 is a schematic external view of a configuration of a multi-blade
20 centrifugal air-sending device according to Embodiment 1 as viewed in a direction
parallel to a rotational axis.
[Fig. 2] Fig. 2 is a sectional view in which a section of the multi-blade centrifugal
air-sending device in Fig. 1 along line A-A is schematically illustrated.
[Fig. 3] Fig. 3 is a schematic view of a configuration of an impeller of the multi25 blade centrifugal air-sending device in Fig. 1 as viewed in a direction parallel to a
rotational axis.
[Fig. 4] Fig. 4 is a sectional view in which a section of the impeller in Fig. 3 along
line B-B is schematically illustrated.
[Fig. 5] Fig. 5 schematically illustrates a positional relationship between a bell
30 mouth and the impeller in Fig. 2.
5
[Fig. 6] Fig. 6 is a partial perspective view in which a portion of an outer
peripheral portion of the impeller in Fig. 3 is enlarged.
[Fig. 7] Fig. 7 is a schematic view of a configuration of a blade of a multi-blade
centrifugal air-sending device according to Embodiment 2 as viewed in a direction
5 parallel to a rotational axis.
[Fig. 8] Fig. 8 is a view of a modification of the blade in Fig. 7.
Description of Embodiments
[0009]
Hereinafter, a multi-blade centrifugal air-sending device 100 according to an
10 embodiment will be described with reference to the drawings. In the following
drawings including Fig. 1, relative dimensional relationships, shapes, and others of
constituent members may differ from actual ones. Members having identical signs in
the following drawings are identical or correspond to each other, which is common to
the entire content of the description. For ease of understanding, terms indicating
15 directions (for example, "upper", "lower", "forward", "rearward", and the other similar
terms) are used, as appropriate. These terms are, however, merely thus used for
convenience of description and are not intended to limit the arrangements and
orientations of a device or components.
[0010]
20 Embodiment 1
Fig. 1 is a schematic external view of a configuration of the multi-blade centrifugal
air-sending device 100 according to Embodiment 1 as viewed in a direction parallel to a
rotational axis RS. Fig. 2 is a sectional view in which a section of the multi-blade
centrifugal air-sending device 100 in Fig. 1 along line A-A is schematically illustrated.
25 With reference to Fig. 1 and Fig. 2, a basic structure of the multi-blade centrifugal airsending device 100 will be described.
[0011]
As illustrated in Fig. 1, the multi-blade centrifugal air-sending device 100 is an airsending device of a multi-blade centrifugal type and includes an impeller 10 that
30 generates an airflow, and a scroll casing 20 that houses the impeller 10. The impeller
6
10 includes, as illustrated in Fig. 1, a back plate 11 having a disk shape, a plurality of
blades 12 each having a uniform thickness, and a rim 13 having an annular shape as
illustrated in Fig. 2. The back plate 11 is provided with a shaft portion 11b to which a
motor (not illustrated) is connected. The plurality of blades 12 are arranged at a
5 peripheral portion of the back plate 11 in the circumferential direction. The rim 13 is
disposed to face the back plate 11 and fixes the plurality of blades 12.
[0012]
As illustrated in Fig. 1, the scroll casing 20 includes a scroll portion 21 and a
discharge portion 22 having a discharge port 22b for air, and rectifies an airflow blown
10 out from the impeller 10 in the centrifugal direction. The scroll casing 20 has a spiral
shape, and an air passage 20a expanding gradually toward the discharge port 22b is
formed in the inside of the scroll casing 20.
[0013]
The scroll portion 21 forms the air passage 20a that converts a dynamic pressure
15 of the airflow generated by the rotation of the impeller 10 into a static pressure. The
scroll portion 21 includes a side wall 23 covering the impeller 10 in the axial direction of
an imaginary rotational axis RS of the impeller 10, and a peripheral wall 24 surrounding
the impeller 10 from the outer side in the radial direction of the rotational axis RS.
Each side wall 23 has an air inlet 23b through which air is sucked. The scroll portion
20 21 also includes a tongue portion 25 positioned between the discharge portion 22 and a
winding start portion 24a of the peripheral wall 24 and constituting a curved surface.
The tongue portion 25 is configured to guide the airflow blown out from the impeller 10
in the centrifugal direction in the vicinity of the winding start portion 24a, to be in a
rotational direction R of the impeller 10 to move toward the discharge port 22b via the
25 scroll portion 21.
[0014]
The radial direction of the rotational axis RS is a direction perpendicular to the
axial direction of the rotational axis RS. An internal space of the scroll portion 21
constituted by the peripheral wall 24 and the side wall 23 serves as the above-described
7
air passage 20a. In the air passage 20a, the airflow blown out from the impeller 10
flows along the peripheral wall 24.
[0015]
In the example illustrated in Fig. 2, the multi-blade centrifugal air-sending device
5 100 is a double-suction-type centrifugal air-sending device configured to suck air from
both end sides in the axial direction of the imaginary rotational axis RS of the impeller
10. The side wall 23 are disposed on both sides of the impeller 10 in the axial direction
of the rotational axis RS of the impeller 10. Each side wall 23 of the scroll casing 20
has the air inlet 23b to enable air to circulate between the impeller 10 and the outside of
10 the scroll casing 20. As illustrated in Fig. 1, the air inlet 23b has a circular shape, and
the impeller 10 is disposed in the scroll casing 20 such that the center of the air inlet
23b and the center of the shaft portion 11b of the impeller 10 substantially coincide with
each other. The impeller 10 is supported about an axis by the scroll casing 20 to be
rotatable.
15 [0016]
As illustrated in Fig. 2, the scroll casing 20 is a casing of a double suction type
having, on both sides of the back plate 11 in the axial direction of the rotational axis RS
of the impeller 10, the side wall 23 having the air inlet 23b. The two side walls 23 are
provided to face each other with the peripheral wall 24 interposed therebetween in the
20 scroll casing 20.
[0017]
As illustrated in Fig. 1, the air inlet 23b provided in each side wall 23 is formed by
a bell mouth 26. That is, the bell mouth 26 forms the air inlet 23b in communication
with a space formed by the back plate 11 and the plurality of blades 12 in the impeller
25 10. In the following description, the space formed by the back plate 11 and the plurality
of blades 12 may be referred to as a flow passage 11a of the impeller 10.
[0018]
As illustrated in Fig. 2, the bell mouth 26 rectifies the air sucked through the air
inlet 23b of each side wall 23 and causes the air to flow into a central portion of the
30 impeller 10 through an impeller air inlet 10a. The bell mouth 26 is provided to project
8
from the side wall 23 toward the inside. More specifically, the bell mouth 26 is formed
such that the opening diameter thereof decreases gradually from the side wall 23 of the
scroll casing 20 toward the inside. With such a configuration, when the impeller 10
rotates, the air in the vicinity of the air inlet 23b of each side wall 23 flows smoothly
5 along the bell mouth 26 and flows into the impeller 10 efficiently through the impeller air
inlet 10a. The impeller air inlet 10a for causing a gas to flow into the flow passage 11a
of the impeller 10 is provided on the side of the rim 13 in the impeller 10.
[0019]
As illustrated in Fig. 1, the peripheral wall 24 is constituted by a wall surface
10 curved in the rotational direction R of the impeller 10. The peripheral wall 24 is
present, as illustrated in Fig. 2, between the two side walls 23 facing each other in the
scroll casing 20 and is provided, as illustrated in Fig. 1, to connect portions of the outer
peripheral edges of the two side walls 23 to each other. The peripheral wall 24 has a
curved inner peripheral surface 24c and guides the airflow blown out to the air passage
15 20a in the scroll portion 21 from the impeller 10, so as to flow along the inner peripheral
surface 24c to the discharge port 22b.
[0020]
The peripheral wall 24 has a configuration in which the wall surface curved as
illustrated in Fig. 1 extends parallel to the axial direction of the rotational axis RS of the
20 impeller 10 as illustrated in Fig. 2. The peripheral wall 24 may have a form inclined
with respect to the axial direction of the rotational axis RS of the impeller 10, and is not
limited to having the form disposed parallel to the axial direction of the rotational axis
RS.
[0021]
25 As illustrated in Fig. 1, the peripheral wall 24 covers the impeller 10 from the
outer side in the radial direction of the shaft portion 11b of the impeller 10, and the inner
peripheral surface 24c of the peripheral wall 24 faces end portions of the plurality of
later-described blades 12 on the outer peripheral side. That is, the inner peripheral
surface 24c of the peripheral wall 24 faces the air blowing-out side of the blades 12 of
30 the impeller 10. The peripheral wall 24 is provided to extend in the rotational direction
9
R of the impeller 10 from the winding start portion 24a positioned at the boundary
between the peripheral wall 24 and the tongue portion 25 to a winding end portion 24b
positioned at the boundary between the discharge portion 22 and the scroll portion 21
on the side away from the tongue portion 25. The winding start portion 24a is, of the
5 peripheral wall 24 constituted by the curved wall surface, an end portion on the
upstream side of the airflow generated by the rotation of the impeller 10, and the
winding end portion 24b is an end portion of the peripheral wall 24 on the downstream
side of the airflow generated by the rotation of the impeller 10. More specifically, the
peripheral wall 24 has a spiral shape. The spiral shape is, for example, a logarithmic
10 spiral, an Archimedes' spiral, or a spiral shape based on an involute curve or any other
curve. With such a configuration, the airflow blown out from the impeller 10 into the air
passage 20a of the scroll casing 20 flows in the gap between the impeller 10 and the
peripheral wall 24 smoothly to the direction of the discharge portion 22. Therefore, the
static pressure of air increases in the rotational direction R of the impeller 10 from the
15 tongue portion 25 toward the discharge portion 22 in the scroll casing 20.
[0022]
The discharge portion 22 forms the discharge port 22b through which the airflow
that has been generated by the rotation of the impeller 10 and passed through the air
passage 20a of the scroll portion 21 is discharged. The discharge portion 22 is
20 constituted by a hollow pipe whose section orthogonal to the flow direction of
discharged air has a rectangular shape. The discharge portion 22 is constituted by, for
example, plate-shaped four side surfaces. Specifically, the discharge portion 22
includes an extended plate 221 smoothly connected to the winding end portion 24b of
the peripheral wall 24, and a diffuser plate 222 extending from the tongue portion 25 to
25 face the extended plate 221. The discharge portion 22 also includes a first side wall
portion and a second side wall portion (not illustrated) each extended from a
corresponding one of the two side walls 23 to connect both ends of the extended plate
221 and the diffuser plate 222 in the axial direction of the rotational axis RS to each
other. The sectional shape of the discharge portion 22 is not limited to a rectangular
30 shape. The discharge portion 22 forms a discharge-side air passage 22a that guides
10
the airflow discharged from the impeller 10 and flowing through the gap between the
peripheral wall 24 and the impeller 10, to be discharged to the outside of the scroll
casing 20.
[0023]
5 The tongue portion 25 is formed between the diffuser plate 222 of the discharge
portion 22 and the winding start portion 24a of the peripheral wall 24 in the scroll casing
20. The tongue portion 25 is formed to have a predetermined radius of curvature, and
the peripheral wall 24 is smoothly connected to the diffuser plate 222 with the tongue
portion 25 interposed therebetween. The tongue portion 25 suppresses the inflow of
10 air from the winding end portion to the winding start portion of the spiral air passage 20a
formed in the inside of the scroll casing 20. In other words, the tongue portion 25 has
a role of separating the airflow flowing from an upstream portion of the air passage 20a
in the rotational direction R of the impeller 10 and the airflow flowing from a downstream
portion of the air passage 20a toward the discharge port 22b in a discharge direction
15 from each other. The static pressure of the airflow flowing into the discharge-side air
passage 22a of the discharge portion 22 increases while the airflow passes through the
scroll casing 20, to be higher than in the scroll casing 20. The tongue portion 25 is
thus configured to have a function of partitioning such different pressures.
[0024]
20 Fig. 3 is a schematic view of a configuration of the impeller 10 of the multi-blade
centrifugal air-sending device 100 in Fig. 1 as viewed in a direction parallel to the
rotational axis RS. In Fig. 3, a portion of each blade 12 covered by the rim 13 is
indicated by a dashed line. Fig. 4 is a sectional view in which a section of the impeller
10 in Fig. 3 along line B-B is schematically illustrated. As illustrated in Fig. 3, the
25 impeller 10 is a centrifugal impeller. The impeller 10 is constituted by a metal and, for
example, constituted by a plurality of steel sheets or other members. The impeller 10
is configured to be driven to rotate by, for example, a motor (not illustrated) and to
forcibly send air in the centrifugal direction, that is, radially outward by a centrifugal
force generated by rotating and suck air through the impeller air inlet 10a provided on
11
the side of the rim 13. The impeller 10 is rotated by, for example, a motor in the
rotational direction R.
[0025]
As illustrated in Fig. 4, the back plate 11 may be formed to have a disk shape in
5 which the wall thickness thereof increases toward the center in the radial direction with
the rotational axis RS as the center, or may be formed to have a thickness that is
constant in the radial direction with the rotational axis RS as the center. As long as the
back plate 11 has a plate shape, the shape of the back plate 11 may be a shape other
than a circular shape and may be, for example, a polygonal shape or any other shape.
10 A motor (not illustrated) is connected to the shaft portion 11b provided at a center
portion of the back plate 11, and the back plate 11 is driven to rotate by the motor via
the shaft portion 11b.
[0026]
As illustrated in Fig. 3, the plurality of blades 12 are disposed in the
15 circumferential direction of a plate surface 111 of the back plate 11 with the rotational
axis RS as the center such that a predetermined interval is formed between mutually
adjacent blades 12. The plurality of blades 12 disposed at the back plate 11 form the
cylindrical shape of the impeller 10. A gap G formed between mutually adjacent blades
12 constitutes the flow passage 11a of the impeller 10.
20 [0027]
Each of the plurality of radially provided blades 12 includes a sirocco blade
portion 30 constituted by a forward blade, and a turbo blade portion 40 constituted by a
rearward blade. The turbo blade portion 40 is connected to the sirocco blade portion
30 in the radial direction, and each blade 12 has a shape curved in the radial direction.
25 The turbo blade portion 40 is provided on the inner peripheral side with respect to the
sirocco blade portion 30 to be continuous with the sirocco blade portion 30. The
sirocco blade portion 30 and the turbo blade portion 40 are smoothly connected to each
other at a blade boundary 12b between the sirocco blade portion 30 and the turbo blade
portion 40.
30 [0028]
12
As illustrated in Fig. 3 and Fig. 4, in the rotation of the back plate 11 about the
rotational axis RS, an end surface of each blade 12 on the inner peripheral side is a
blade leading edge 12f, and an end surface of each blade 12 on the outer peripheral
side is a blade trailing edge 12r. In the following description, the blade leading edge
5 12f may be referred to as the inner peripheral edge of the blade 12. In the example
illustrated in Fig. 3, the turbo blade portion 40 is linearly formed from the blade
boundary 12b to the blade leading edge 12f in the radial direction. As illustrated in Fig.
4, the blade leading edge 12f is inclined with respect to the axial direction of the
rotational axis RS such that the blade leading edge 12f gradually approaches the
10 rotational axis RS from the side of the rim 13 toward the side of the back plate 11 in the
axial direction of the rotational axis RS. The blade trailing edge 12r and the blade
boundary 12b are each substantially parallel to the rotational axis RS. The detailed
configuration of each of the blades 12 will be described later.
[0029]
15 As illustrated in Fig. 4, each of the plurality of blades 12 is provided between the
back plate 11 and the rim 13 in the axial direction of the rotational axis RS. In the axial
direction of the rotational axis RS, one end of each of the blades 12 is connected to the
back plate 11, and the other end of each of the blades 12 is connected to the rim 13.
The other end of each of the blades 12 extends along the rim 13 in the radial direction
20 and further extends toward the inner side than an inner peripheral end 13a of the rim
13. That is, a portion of the other end of each of the blades 12 on the inner peripheral
side is not connected to the rim 13.
[0030]
In the following description, the one end of each blade 12 connected to the back
25 plate 11 and the other end of the blade 12 on the side of the rim 13 in the axial direction
of the rotational axis RS may be referred to as an end portion 12d on the side of the
back plate 11 and an end portion 12u on the side of the rim 13, respectively. In
addition, in the following description, a portion of the blade leading edge 12f of each of
the blades 12 connected to the end portion 12d on the side of the back plate 11 is
30 referred to as a main-plate-side inner peripheral end 12fd, and a portion of the blade
13
leading edge 12f of each of the blades 12 connected to the end portion 12u on the side
of the rim 13 is referred to as a side-plate-side inner peripheral end 12fu. In Fig. 3, a
first imaginary circle C1 passing through the side-plate-side inner peripheral ends 12fu
of the plurality of blades 12 is indicated by a dashed dotted line. The first imaginary
5 circle C1 has the center at the imaginary rotational axis RS of the back plate 11.
[0031]
As illustrated in Fig. 4, a portion of each blade 12 extends toward the inner side
further than the inner peripheral end 13a of the rim 13 from the side of the back plate 11
to the side of the rim 13. In other words, as illustrated in Fig. 3, not only the main10 plate-side inner peripheral ends 12fd but also the side-plate-side inner peripheral ends
12fu (indicated by the first imaginary circle C1) of the blades 12 are positioned on the
inner side with respect to the inner peripheral end 13a of the rim 13. That is, a blade
portion of each blade 12 including a portion of the end portion 12u on the inner
peripheral side and the entirety of the blade leading edge 12f is exposed via the inner
15 peripheral end 13a of the rim 13.
[0032]
The rim 13 maintains the positional relationship of the tips of the blades 12 and
reinforces the plurality of blades 12. In the example illustrated in Fig. 4, the rim 13 and
the plurality of blades 12 are provided on both sides of the back plate 11 in the axial
20 direction of the rotational axis RS. The rim 13 provided to face the plate surface 111 of
the back plate 11 on one side couples the plurality of blades 12 disposed on the side of
the plate surface 111 of the back plate 11 on the one side to each other. The rim 13
provided to face a plate surface 112 of the back plate 11 on the other side couples the
plurality of blades 12 disposed on the side of the plate surface 112 of the back plate 11
25 on the other side to each other.
[0033]
As illustrated in Fig. 2, the impeller 10 is disposed in the scroll casing 20 such
that the center of the air inlet 23b coincides with the center of the shaft portion 11b of
the impeller 10 and that the rim 13 of the impeller 10 faces the side wall 23 each having
30 the air inlet 23b. In the radial direction, the inner peripheral end of each of the side wall
14
23, that is, the opening edge of the air inlet 23b of the side wall 23 substantially
coincides with the inner peripheral end 13a of the rim 13 of the impeller 10. Therefore,
a blade portion of the impeller 10 extending toward the inner side further than the inner
peripheral end 13a of the rim 13 is exposed from the inner peripheral end of the side
5 wall 23 of the scroll casing 20.
[0034]
Fig. 5 schematically illustrates a positional relationship between the bell mouth 26
and the impeller 10 in Fig. 2. As illustrated in Fig. 5, the inner peripheral end 13a of
the rim 13 is preferably positioned on the inner peripheral side with respect to the outer
10 peripheral end 26a of the tip of the bell mouth 26. With such a configuration, the length
of the rim 13 in the radial direction is ensured so that the plurality of blades 12 are
sufficiently fixed by the rim 13.
[0035]
Fig. 6 is a partial perspective view in which a portion of an outer peripheral
15 portion of the impeller 10 in Fig. 3 is enlarged. Hereinafter, with the side of the rim 13
and the side of the back plate 11 in the axial direction of the rotational axis RS being
defined as the upper side and the lower side, respectively, a detailed configuration of
the blades 12 will be described with reference to Fig. 3, Fig. 4, and Fig. 6.
[0036]
20 As illustrated in Fig. 3, Embodiment 1 is configured such that the blade boundary
12b of each of the blades 12 coincides with the inner peripheral end 13a of the rim 13 in
the radial direction, the sirocco blade portion 30 of each of the blades 12 is covered by
the rim 13, and the turbo blade portion 40 of each of the blades 12 is exposed from the
inner peripheral end 13a of the rim 13. By covering, with the rim 13, the sirocco blade
25 portion 30 that increases the air velocity of an airflow compared with the turbo blade
portion 40, it is possible to suppress an increase of noise.
[0037]
As illustrated in Fig. 4, the blade leading edge 12f is inclined such that a distance
Ld between the inner peripheral end 13a of the rim 13 and the main-plate-side inner
30 peripheral end 12fd of the blade leading edge 12f is larger than a distance Lu between
15
the inner peripheral end 13a of the rim 13 and the side-plate-side inner peripheral end
12fu of the blade leading edge 12f. That is, the blade leading edge 12f is inclined such
that the inner diameter formed by the blade leading edges 12f of the plurality of blades
12 increases gradually from the side of the back plate 11 toward the side of the rim 13.
5 [0038]
As illustrated in Fig. 6, the turbo blade portion 40 includes a first turbo blade
portion 41 connected to the sirocco blade portion 30, and a second turbo blade portion
42 on the inner peripheral side with respect to the first turbo blade portion 41. The first
turbo blade portion 41 includes the entirety of the upper surface of the turbo blade
10 portion 40 and has, for example, a quadrangular shape such as a rectangular shape.
The second turbo blade portion 42 includes the entirety of the blade leading edge 12f of
the blade 12 and has a triangular shape. That is, the turbo blade portion 40 is formed
such that the chord length of the turbo blade portion 40 increases from the side of the
rim 13 toward the side of the back plate 11.
15 [0039]
In the example illustrated in Fig. 6, in the radial direction, the side-plate-side inner
peripheral end 12fu of the blade leading edge 12f is positioned on the inner side with
respect to the inner peripheral end 13a of the rim 13, and the blade boundaries 12b of
the blades 12 indicated by the first imaginary circle C1 are positioned at the inner
20 peripheral end 13a of the rim 13. That is, in the example illustrated in Fig. 6, the
entirety of the turbo blade portion 40 including the first turbo blade portion 41 and the
second turbo blade portion 42 is configured to be disposed on the inner side with
respect to the inner peripheral end 13a of the rim 13 and exposed. Meanwhile, the
entirety of the upper surface of the sirocco blade portion 30 is covered by the rim 13.
25 [0040]
In the radial direction, the position of the blade boundary 12b of each blade 12
does not necessarily coincide with the position of the inner peripheral end 13a of the rim
13. In the radial direction, as long as at least a portion of the first turbo blade portion
41 extends toward the inner side further than the inner peripheral end 13a of the rim 13,
16
air can be taken from the side of the back plate 11 toward the side of the rim 13 in the
flow passage 11a by an exposed portion of the turbo blade portion 40.
[0041]
As illustrated in Fig. 3, each of the blades 12 has a wall thickness W that is
5 constant in the radial direction. As illustrated in Fig. 6, each of the blades 12 has the
wall thickness W that is constant from the side of the back plate 11 (refer to Fig. 3) to
the side of the rim 13. Each of the blades 12 can be constituted by a steel sheet
having a uniform thickness. That is, the wall thickness W of each blade 12 at the end
portion 12u on the side of the rim 13 is identical to the wall thickness W of the blade 12
10 at the end portion 12d (Fig. 6) on the side of the back plate 11. Therefore, the gap G
formed between adjacent blades 12 increases gradually from the blade leading edge
12f toward the blade trailing edge 12r and has the same size from the side of the back
plate 11 to the side of the rim 13.
[0042]
15 With reference to Fig. 1 to Fig. 6, operation of the multi-blade centrifugal airsending device 100 will be described. As illustrated in Fig. 1, when the impeller 10 is
driven to rotate about the rotational axis RS by a motor (not illustrated), air outside the
multi-blade centrifugal air-sending device 100 flows into a central portion of the impeller
10 in the axial direction through the air inlets 23b of the scroll casing 20 and the impeller
20 air inlet 10a. The air that has flowed into the central portion of the impeller 10 is taken
into the flow passage 11a of the impeller 10 from the blade leading edges 12f due to the
rotation of the impeller 10 and flows radially outward in the flow passage 11a.
[0043]
As described with reference to Fig. 3 and Fig. 4, the portion of each blade 12
25 including portions on the side of the back plate 11 and the side of the rim 13 is exposed
on the inner side from the inner peripheral ends of the side wall 23 and the inner
peripheral end 13a of the rim 13. Therefore, compared with a configuration in which
only a portion of each blade 12 on the side of the back plate 11 extends, the air that has
flowed into a central portion of the impeller 10 can be taken into the flow passage 11a
30 also from the side of the rim 13 at the blade leading edge 12f, and the suction air
17
volume can be increased not only on the side of the back plate 11 but also on the side
of the rim 13.
[0044]
As illustrated in Fig. 4, the blade leading edge 12f is inclined, and the side-plate5 side inner peripheral end 12fu is positioned on the outer side in the radial direction with
respect to the main-plate-side inner peripheral end 12fd. It is thus possible to reduce
resistance on the side of the rim 13 at the blade portion exposed from the inner
peripheral end 13a of the rim 13 and possible to suppress an increase of noise. In
addition, by reducing the resistance on the side of the rim 13 at the exposed blade
10 portion, the inflow loss of the airflow sucked through the impeller air inlet 10a is
reduced, and air can be induced also on the side of the back plate 11. It is thus
possible to suppress a decrease in the suction air volume on the side of the back plate
11 with respect to the side of the rim 13.
[0045]
15 As illustrated in Fig. 6, since the wall thickness W of each of the blades 12 of
the impeller 10 constituted by a metal is uniform, the gap G formed between adjacent
blades 12 is constant from the side of the back plate 11 to the side of the rim 13.
Therefore, compared with an impeller constituted by a resin material as in the related
art and in which the gap G is narrow on the side of the back plate 11, the suction air
20 volume can be increased also on the side of the back plate 11 in the impeller 10.
[0046]
As illustrated in Fig. 6, the turbo blade portion 40 is provided on the inner side of
the sirocco blade portion 30 in the radial direction in each blade 12, and the turbo blade
portion 40 is configured to be exposed from the inner peripheral end 13a of the rim 13.
25 Therefore, the air that has been taken into the flow passage 11a formed by the turbo
blade portion 40 and inclining in a direction opposite to the rotation direction of the
impeller while gradually expanding toward the sirocco blade portion 30 is sent to the
sirocco blade portion 30 while being efficiently pressurized.
[0047]
18
The pressurized airflow that has reached the blade boundary 12b with respect to
the sirocco blade portion 30 then flows along the sirocco blade portion 30 in the flow
passage 11a toward the blade trailing edge 12r while changing the traveling direction
thereof. Thereafter, the airflow that has reached the blade trailing edge 12r is sent to
5 the air passage 20a of the scroll casing 20 from the flow passage 11a of the impeller 10.
The airflow that has been sent to the air passage 20a from the impeller 10 is further
pressurized when passing through the air passage 20a that has a spiral shape and that
expands toward the discharge port 22b and is blown out to the outer peripheral side
through the discharge port 22b.
10 [0048]
In Embodiment 1, the multi-blade centrifugal air-sending device 100 that is a
double-suction-type centrifugal air-sending device has been described. The multiblade centrifugal air-sending device 100, however, may be a single-suction-type
centrifugal air-sending device. The number of the blades 12 is not limited to that in the
15 drawings.
[0049]
As described above, the multi-blade centrifugal air-sending device 100 according
to Embodiment 1 includes the impeller 10, and the spiral scroll casing 20 housing the
impeller 10. The impeller 10 includes the back plate 11 having a disk shape; the
20 plurality of blades 12 arranged at the peripheral portion of the back plate 11 in the
circumferential direction; and the annular rim 13 disposed to face the back plate 11 and
fixing the plurality of blades 12. The scroll casing 20 is configured such that air is
introduced from the side of the rim 13 and blown out to the outer peripheral side. The
impeller 10 is constituted by a metal, and each blade 12 has the wall thickness W that is
25 constant from the side of the back plate 11 to the side of the rim 13. Each blade 12
extends toward the inner side further than the inner peripheral end 13a of the rim 13
from the side of the back plate 11 to the side of the rim 13.
[0050]
According to the present disclosure, since the impeller 10 is constituted by a
30 metal and the wall thickness W of each blade 12 is constant from the side of the rim 13
19
to the side of the back plate 11, it is possible to ensure the gap G that is the same as
that on the side of the rim 13 also on the side of the back plate 11 in the impeller 10.
Therefore, compared with a multi-blade centrifugal air-sending device that is a resin
molded product as in the related art, the suction air volume can be increased also on
5 the side of the back plate 11 in the impeller 10.
[0051]
The inner peripheral edge (blade leading edge 12f) of each blade 12 is inclined
from the side of the rim 13 toward the side of the back plate 11. The distance Ld
between the inner peripheral end 13a of the rim 13 and the inner peripheral end (main10 plate-side inner peripheral end 12fd) of the blade leading edge 12f on the side of the
back plate 11 is larger than the distance Lu between the inner peripheral end 13a of the
rim 13 and the inner peripheral end (side-plate-side inner peripheral end 12fu) of the
blade leading edge 12f on the side of the rim 13. In other words, the blade leading
edge 12f is inclined such that a distance in the radial direction between the main-plate15 side inner peripheral end 12fd and the rotational axis RS (or a perpendicular line
extending from the inner peripheral end 13a of the rim 13 to the back plate 11) of the
impeller 10 is larger than a distance in the radial direction between the side-plate-side
inner peripheral end 12fu and the rotational axis RS (or a perpendicular line extending
from the inner peripheral end 13a of the rim 13 to the back plate 11) of the impeller 10.
20 [0052]
Consequently, it is possible to reduce the resistance generated on the side of the
rim 13 at the blade portion exposed from the inner peripheral end 13a of the rim 13 and
possible to suppress the inflow loss of the air flowing in through the impeller air inlet 10a
and generation of, for example, a noise increase due to resistance. It is thus possible
25 to induce the air that flows in through the impeller air inlet 10a also to the side of the
back plate 11 and possible to suppress a decrease in the suction air volume on the side
of the back plate 11 with respect to the side of the rim 13.
[0053]
Each blade 12 includes the sirocco blade portion 30 constituted by the forward
30 blade, and the turbo blade portion 40 connected to the inner peripheral side of the
20
sirocco blade portion 30 and constituted by the rearward blade. The turbo blade
portion 40 of each blade 12 is provided on the inner side with respect to the inner
peripheral end 13a of the rim 13. Consequently, the area of the exposed blade portion
can be further increased, and an increased amount of the air that flows in through the
5 impeller air inlet 10a can be taken into the gap G between the blades 12. In addition,
the air that has been taken into the flow passage 11a formed by the turbo blade portion
40 and inclining in the direction opposite to the rotational direction R of the impeller 10
while expanding gradually toward the outer side in the radial direction can be sent to the
sirocco blade portion 30 highly efficiently while being pressurized.
10 [0054]
The scroll casing 20 includes the facing side wall 23 where the air inlet 23a is
provided, the peripheral wall 24, and the bell mouth 26 forming the air inlet 23a and
whose opening diameter gradually decreases toward the inside. The inner peripheral
end 13a of the rim 13 is positioned on the inner peripheral side with respect to the outer
15 peripheral end 26a of the tip of the bell mouth 26. Consequently, the length of the rim
13 in the radial direction is ensured, and the plurality of blades 12 can be more reliably
fixed by the rim 13.
[0055]
Embodiment 2
20 Fig. 7 is a schematic view of a configuration of a blade of a multi-blade centrifugal
air-sending device according to Embodiment 2 as viewed in a direction parallel to a
rotational axis. Embodiment 2 differs from Embodiment 1 in that, when each blade 12
is viewed in the axial direction of the rotational axis RS of the impeller 10, a portion of
the first turbo blade portion 41 is covered by the rim 13. In Fig. 7, the position of the
25 inner peripheral end 13a of the rim 13 with respect to each blade 12 set at the plate
surface 111 (refer to Fig. 3) of the back plate 11 is indicated by a dashed double-dotted
line. In addition, in Fig. 7, the direction of the airflow passing the vicinity of a suction
surface 122 of each blade 12 during rotation of the impeller 10 is indicated by the arrow
F1.
30 [0056]
21
Also in Embodiment 2, the first turbo blade portion 41 includes the entirety of
the upper surface of the turbo blade portion 40 and has a quadrangular shape, and
the second turbo blade portion 42 includes the entirety of the blade leading edge 12f
of the blade 12 and has a triangular shape, as in Embodiment 1. In Embodiment 2,
5 the side-plate-side inner peripheral end 12fu of the blade leading edge 12f at the
boundary between the first turbo blade portion 41 and the second turbo blade portion
42 is positioned on the inner side with respect to the position of the inner peripheral
end 13a of the rim 13, as in Embodiment 1.
[0057]
10 In Embodiment 2, the blade boundary 12b between the sirocco blade portion 30
and the first turbo blade portion 41 of the turbo blade portion 40 is positioned on the
outer side with respect to the position of the inner peripheral end 13a of the rim 13,
and the sirocco blade portion 30 and a portion of the first turbo blade portion 41 on the
outer peripheral side are configured to be covered by the rim 13. In other words, a
15 portion of each blade 12 covered by the rim 13 is constituted by the sirocco blade
portion 30 and a portion of the first turbo blade portion 41 on the outer peripheral side.
[0058]
Therefore, the volume of air sucked into the flow passage 11a can be increased
by the portion of the turbo blade portion 40 exposed from the rim 13, and the airflow
20 sucked into the flow passage 11a can be efficiently pressurized by the portion of the
turbo blade portion 40 covered by the rim 13.
[0059]
When viewed in the axial direction of the rotational axis RS of the impeller 10, the
percentage of a chord length L2 of the portion of the first turbo blade portion 41 covered
25 by the rim 13 with respect to a chord length L1 of the portion of each blade 12 covered
by the rim 13 is preferably larger than 0% and less than or equal to 30%.
[0060]
Fig. 8 is a view of a modification of the blade 12 in Fig. 7. In the modification
illustrated in Fig. 8, the percentage of the chord length L2 of the portion of the first turbo
30 blade portion 41 covered by the rim 13 with respect to the chord length L1 of the portion
22
of each blade 12 covered by the rim 13 is 40%, which is larger than 30%. To set the
percentage of the chord length L2 with respect to the chord length L1 to more than 30%
as in the modification, when the blade chord length of each blade 12 is constant, it is
necessary to decrease the chord length of the sirocco blade portion 30 and further
5 incline the sirocco blade portion 30 with respect to the turbo blade portion 40 in the
rotational direction R. Consequently, a separation vortex Fa may be generated on the
side of the suction surface 122 of the sirocco blade portion 30, which may lead to a
decrease in the air volume as a result of the airflow separating from the suction surface
122 and to an increase of noise due to the generation of the separation vortex Fa.
10 [0061]
In Embodiment 2, each blade 12 includes the sirocco blade portion 30
constituted by the forward blade, and the turbo blade portion 40 connected to the inner
peripheral side of the sirocco blade portion 30 and constituted by the rearward blade.
When viewed in the axial direction of the rotational axis RS of the impeller 10, the
15 portion of each blade 12 covered by the rim 13 is constituted by the sirocco blade
portion 30 and a portion of the turbo blade portion 40. The chord length of the
sirocco blade portion 30, that is, the difference between the chord length L1 and the
chord length L2 is larger than the chord length L2 of a portion of the turbo blade
portion 40. Further, the percentage of the chord length L2 of the portion (the portion
20 of the turbo blade portion 40 described above) of the turbo blade portion 40 covered
by the rim 13 with respect to the chord length L1 of the portion of each blade 12
covered by the rim 13 is more than 0% and less than or equal to 30%.
[0062]
Consequently, when an airflow F2 flows from the turbo blade portion 40 to the
25 sirocco blade portion 30, a sudden change in the angle of the airflow can be
suppressed in a process in which the angle of each blade 12 changes. It is thus
possible to suppress separation occurring at the suction surface 122. As a result, it
is possible to suppress a decrease in the air volume due to the airflow separating from
the suction surface 122 and an increase of noise due to generation of the separation
30 vortex Fa.
23
[0063]
Note that the embodiments can be combined together, and modifications and
omissions can be performed, as appropriate, in each embodiment.
Reference Signs List
5 [0064]
10: impeller, 10a: impeller air inlet, 11: back plate, 11a: flow passage, 11b: shaft
portion, 12: blade, 12b: blade boundary, 12d: end portion, 12f: blade leading edge, 12fd:
main-plate-side inner peripheral end, 12fu: side-plate-side inner peripheral end, 12r:
blade trailing edge, 12u: end portion, 13: rim, 13a: inner peripheral end, 20: scroll
10 casing, 20a: air passage, 21: scroll portion, 22: discharge portion, 22a: discharge-side
air passage, 22b: discharge port, 23: side wall, 23b: air inlet, 24: peripheral wall, 24a:
winding start portion, 24b: winding end portion, 24c: inner peripheral surface, 25: tongue
portion, 26: bell mouth, 26a: outer peripheral end, 30: sirocco blade portion, 40: turbo
blade portion, 41: first turbo blade portion, 42: second turbo blade portion, 100: multi15 blade centrifugal air-sending device, 111: plate surface, 112: plate surface, 122: suction
surface, 221: extended plate, 222: diffuser plate, C1: first imaginary circle, F1: arrow,
F2: airflow, Fa: separation vortex, G: gap, L1: chord length, L2: chord length, Ld:
distance, Lu: distance, R: rotation direction, RS: rotational axis, W: wall thickness
24
We Claim :
[Claim 1]
A multi-blade centrifugal air-sending device comprising:
an impeller including a back plate having a disk shape, a plurality of blades
5 arranged at a peripheral portion of the back plate in a circumferential direction, and a
rim having an annular shape and disposed to face the back plate, the rim fixing the
plurality of blades; and
a scroll casing having a spiral shape and housing the impeller, the scroll casing
being configured such that air is introduced from a side of the rim and blown out to an
10 outer peripheral side,
wherein the impeller is constituted by a metal, and
wherein each of the blades has a wall thickness constant from a side of the back
plate to the side of the rim and extends toward an inner side further than an inner
peripheral end of the rim.
15 [Claim 2]
The multi-blade centrifugal air-sending device of claim 1,
wherein an inner peripheral edge of each of the blades is inclined from the side of
the rim toward the side of the back plate such that a distance between the inner
peripheral end of the rim and an inner peripheral end of the inner peripheral edge of
20 each of the blades on the side of the back plate is larger than a distance between the
inner peripheral end of the rim and an inner peripheral end of the inner peripheral edge
of each of the blades on the side of the rim.
[Claim 3]
The multi-blade centrifugal air-sending device of claim 1 or claim 2,
25 wherein each of the blades includes a sirocco blade portion constituted by a
forward blade, and a turbo blade portion constituted by a rearward blade and connected
to an inner peripheral side of the sirocco blade portion,
wherein, when viewed in an axial direction of a rotational axis of the impeller, a
portion of each of the blades covered by the rim is constituted by the sirocco blade
30 portion and a portion of the turbo blade portion, and
25
wherein a chord length of the sirocco blade portion is larger than a chord length
of the portion of the turbo blade portion.
[Claim 4]
The multi-blade centrifugal air-sending device of claim 3,
5 wherein a percentage of the chord length of the portion of the turbo blade portion
with respect to a chord length of the portion of each of the blades is larger than 0% and
less than or equal to 30%.
[Claim 5]
The multi-blade centrifugal air-sending device of claim 1 or claim 2,
10 wherein each of the blades includes a sirocco blade portion constituted by a
forward blade, and a turbo blade portion constituted by a rearward blade and connected
to an inner peripheral side of the sirocco blade portion, and
wherein the turbo blade portion of each of the blades is provided on the inner side
with respect to the inner peripheral end of the rim.
15 [Claim 6]
The multi-blade centrifugal air-sending device of any one of claims 1 to 5,
wherein the scroll casing includes a facing side wall where an air inlet is provided,
a peripheral wall, and a bell mouth forming the air inlet and having an opening diameter
gradually decreasing toward an inside, and
20 wherein the inner peripheral end of the rim is positioned on an inner peripheral
side with respect to an outer peripheral end of a tip of the bell mouth.