Patent Application
20110031786
The present invention relates to a centrifugal air blower including a flat centrifugal multi-blade impeller having a ratio H/D of impeller height H to impeller diameter D of 0.2 or less. The present invention also relates to an automobile seat incorporating such a centrifugal air blower.
Centrifugal air blowers have a configuration in which a centrifugal multi-blade impeller (hereinafter referred to as an “impeller”) is housed in a spiral scroll casing (hereinafter referred to as a “casing”). The impeller radially outwardly blows air that is taken in along the central axis of rotation. The casing converts the dynamic pressure to static pressure while collecting the air blown out of the impeller, and then blows the air from an outlet provided on a spiral end side of the casing.
Patent Document 1 discloses a centrifugal air blower of this type in which a low profile impeller having a ratio H/D (aspect ratio) of impeller height H in a direction of the central axis of rotation to impeller diameter D of 0.5 or less is used, and the minimum spacing (nose gap) between a nose (also referred to as a “tongue”) of the casing and the impeller is 0.08 times or more and 0.2 times or less the impeller diameter D.
Patent Document 1: JP2002-371997A
Vehicle seats for automobiles or the like that incorporate a centrifugal air blower have been proposed in recent years. In this application, there are demands for a seat incorporating a plurality of centrifugal air blowers and for increased passenger compartment space, and in order to respond to the demands, even smaller and lower profile impellers are required.
However, the configuration of Patent Document 1 has a problem in that when a lower profile impeller having an aspect ratio H/D of 0.2 or less is used, the air blowing performance per rotation of the impeller drops significantly.
In addition, there is another problem in that when the number of rotations of the impeller is increased in order to improve the air blowing performance, noise increases.
The present invention has been conceived to solve the above-described problems encountered in conventional technology, and it is an object of the present invention to provide a centrifugal air blower in which both improved air blowing performance and reduced noise are achieved. It is another object of the present invention to provide an automobile seat incorporating such a centrifugal air blower.
A centrifugal air blower according to the present invention includes a centrifugal multi-blade impeller that has a plurality of blades around a central axis of rotation and that radially outwardly blows air taken in along the central axis of rotation and a spiral scroll casing housing the centrifugal multi-blade impeller. A ratio H/D of a height H of the centrifugal multi-blade impeller in a direction of the central axis of rotation to a diameter D of the centrifugal multi-blade impeller is 0.2 or less, and the scroll casing has a logarithmic spiral spread angle γ of 2.0 degrees or more.
An automobile seat according to the present invention incorporates the centrifugal air blower of the present invention.
According to the present invention, because the logarithmic spiral spread angle γ of the casing is set properly, in the centrifugal air blower including the low profile impeller having a ratio H/D of 0.2 or less, the dynamic pressure generated by the impeller is converted to static pressure efficiently by the casing so that the air blowing performance (pressure-air flow characteristics) improves.
As a result of the improved air blowing performance, the number of rotations can be reduced, and consequently noise can be reduced.
Accordingly, with the centrifugal air blower of the present invention, it is possible to improve the air blowing capability per rotation and reduce air blowing noise.
A centrifugal air blower according to the present invention includes an impeller having a plurality of blades and a spiral casing housing the impeller. A driving source (for example, a motor) for rotating the impeller may be incorporated in the casing, or may be disposed outside the casing.
There is no particular limitation on the shape of the blades of the impeller, and the blades may be forward curved blades whose air outlet sections (outer ends) face the direction of rotation, or may be backward curved blades whose air outlet sections face a direction opposite to the direction of rotation. However, it is preferable to use forward curved blades whose outlet sections face the direction of rotation, and the blades preferably have an outlet angle β of 60° or more and 90° or less. This is because the energy that rotates the impeller can be converted to dynamic pressure efficiently.
There is also no particular limitation on the number of blades provided in the impeller.
It is preferable that an annular shroud is provided at an outer periphery on an air intake side of the impeller. With this configuration, due to a rectifying effect of the shroud, it is possible to suppress generation of a vortex resulting from air flow flowing radially outwardly from the impeller as well as backflow to the impeller, so that the blade passing frequency noise can be reduced.
Hereinafter, the present invention will be described in detail using a preferred embodiment. It is to be understood, however, that the present invention is not limited to the embodiment given below.
The centrifugal air blower 1 includes the impeller 10 and the casing 20 housing the impeller 10.
The impeller 10 is rotationally driven about a central axis of rotation 10a in a direction of rotation 10d by an electric motor 30. The impeller 10 includes a number of blades (wings) 11 around the central axis of rotation 10a, and radially outwardly blows air taken in along the central axis of rotation 10a. A shroud 12 sequentially connecting outermost ends of the blades 11 is provided on an air inlet 21 side of the impeller 10 (see
The casing 20 is a spiral scroll casing that collects air blown out of the impeller 10 and at the same time converts the dynamic pressure of the air to static pressure. The air inlet 21 is provided on one side in a direction of the central axis of rotation 10a of the air blower 1 (on the side opposite to the electric motor 30), and an air outlet 22 through which air is blown is provided at the spiral end side.
As shown in
Where the diameter of an imaginary circle defined by inner ends of the blades 11 is represented by D1 (see
It is preferable that the outlet sections of the blades 11 of the impeller 10 face toward the same direction as the direction of rotation 10d of the impeller 10, and in particular, the blades 11 preferably have an outlet angle β of 60° or more and 90° or less. As used herein, the outlet angle β refers to, as shown in
As shown in
r=r
0·exp(θ·tan(γ)),
where r is a distance from the central axis of rotation 10a to the inner wall face of the outer shell of the casing 20,
r0 is a distance from the central axis of rotation 10a to the inner wall face of the outer shell of the casing 20, extending along a reference line L0 connecting a center of curvature Pn of a nose 23 and the central axis of rotation 10a, and
θ is an angle measured from the reference line L0 connecting the center of curvature Pn of the nose 23 and the central axis of rotation 10a in the direction of rotation 10d of the impeller 10.
The technical significance of the logarithmic spiral spread angle γ being 2.0 degrees or more will be described.
Comparison of the working example in which the logarithmic spiral spread angle γ is 2.9 degrees and the comparative example in which the logarithmic spiral spread angle γ is 1.0 degree shows that the centrifugal air blower of the working example exhibits a higher static pressure than the centrifugal air blower of the comparative example at the same flow (φ)=0.14), indicating that the centrifugal air blower of the working example has higher air blowing performance.
Since the centrifugal air blowers of the working example and the comparative example are different only in terms of logarithmic spiral spread angle γ, the spacing (nose gap) between the nose 23 of the casing 20 and the impeller 10 is smaller in the centrifugal air blower of the working example. In centrifugal air blowers, generally, when the nose gap is reduced to improve the air blowing performance, noise (blade passing frequency noise, hereinafter referred to as “NZ noise”) that is generated by the air blown radially outwardly from the impeller impinging on the nose increases.
As can be understood from the above description, according to the present invention, the range of the logarithmic spiral spread angle γ of the casing 20 (the lower limit value in particular) is set properly, and therefore in the centrifugal air blower using the low profile impeller having a small aspect ratio H/D, the dynamic pressure generated by the impeller 10 is converted to static pressure by the casing 20, so that the air blowing performance (pressure-air flow characteristics) improves. In addition, despite the fact that the air blowing performance improves, little harmful NZ noise will be generated.
Generally, in centrifugal air blowers, the air blowing performance improves as the number of rotations of the impeller is increased. The centrifugal air blower of the present invention has superior air blowing performance, and therefore the same level of static pressure as in conventional centrifugal air blowers can be obtained with a number of rotations of the impeller smaller than that of conventional centrifugal air blowers. According to the centrifugal air blower of the present invention, it is therefore possible to reduce the number of rotations of the impeller, and as a result, reduced noise can be achieved.
When the centrifugal air blower is incorporated in an automobile seat (see
In the present invention, there is no particular limitation on the upper limit value of the logarithmic spiral spread angle γ. However, as described above, the larger the logarithmic spiral spread angle γ, the smaller the nose gap, and there is a possibility that NZ noise might become noticeable. For this reason, generally, it is preferable that the logarithmic spiral spread angle γ is 4.0 degrees or less.
As described above, because the centrifugal air blower 1 of the present invention includes the low profile impeller 10 having an aspect ratio H/D of 0.2 or less, the centrifugal air blower 1 is thin. Accordingly, any increase in the thickness of the seating portion 101 and the seat back 102 due to incorporation of the centrifugal air blower 1 will be very small. It is therefore possible to avoid having the interior space of the vehicle become cramped. Also, the centrifugal air blower 1 of the present invention is low noise, so that the passenger will hear little unpleasant noise even when the centrifugal air blower 1 is incorporated in the seat 100.
When incorporating the centrifugal air blower 1 in a limited space such as the seat 100, it is desirable that the maximum outer diameter W (see
The automobile seat is merely one of the fields of application of the centrifugal air blower of the present invention, and the centrifugal air blower of the present invention can have applications other than for automobile seats.
The centrifugal air blower of the present invention is small and low profile, and at the same time has high air blowing capability and is low noise, so that it can especially preferably be used as an air blower disposed in a limited space (for example, a passenger compartment).
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-091289 | Apr 2009 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2010/001652 | 3/9/2010 | WO | 00 | 10/20/2010 |
