Blower

Details Blower Blower

1999-05-13

2001-02-06

Verdier, Christopher (Department: 3745)

Rotary kinetic fluid motors or pumps

Working fluid passage or distributing means associated with...

Vane or deflector

C415S119000, C415S211100, C415S214100, C415S914000, C416S24700A

Reexamination Certificate

active

06183196

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a blower and a method for determining a slit shape for a blower.
BACKGROUND OR THE INVENTION
In recent years, high-density mounting of electrical circuits has been widely used as equipment is miniaturized and becomes electronic. Accordingly, because of the increase in heat density of the electronic equipment, a blower has been used for cooling the equipment.
For a conventional blower, as shown in
FIG. 9
, an annular wall
2
is formed so as to be spaced from the blade tip end of an axial fan
1
, and the axial fan
1
rotates around a shaft
4
in a blowing state in which a motor
3
is energized, by which an air flow (air quantity per unit time)
5
directed from the suction side to the discharge side is generated.
However, in the aforementioned blowing state, the velocity of the air flow increases on the back pressure side of the blade tip end, and a low-energy zone due to the effect of an inter-blade secondary flow is produced on the blade trailing edge side where the air flow is converted into pressure energy. In this zone, loss is great, and the flow is liable to be separated. The air flow is separated from the blade surface, so that vortexes are produced in the separation region, by which turbulence noise is increased, and the noise level and the air flow vs. static pressure characteristics deteriorate.
This phenomenon is frequently found especially when a flow resistance (system impedance) is applied to the discharge flow side and when the occurrence of leakage vortexes at the blade tip end increases, by which the fan goes into a stalling state.
To solve this problem, in a blower disclosed in a prior application (Japanese Patent Application Laid-Open No. 10-18995) filedby the same applicant as that of this invention, a method has been disclosed in which air is sucked to the inside of the annular wall through slits formed in the annular wall in the blowing state to restrain leakage vortexes at the blade tip end and rotating stall, by which the air flow vs. static pressure characteristics are improved and the noise is reduced.
FIGS. 10
a
to
10
c
show a blower as disclosed in Japanese Patent Application Laid-Open No. 10-18995.
For this blower, slits
6
are formed in an annular wall
2
surrounding an axial fan
1
. Specifically, annular plates
7
1
,
7
2
,
7
3
,
7
4
,
7
5
are laminated with spacers
8
being held therebetween, and a slit
6
is formed between the adjacent annular plates of the annular plates
7
1
, . . .
7
5
.
FIG. 11
shows the characteristics of this blower at the same rotational speed.
The blower with slits, in which air is allowed to flow in from the outer periphery of the annular wall
2
, is superior to the conventional (no-slit) blower of the same size in terms of air flow and noise at high pressures. However, the blower with slits has a problem in that the air flow at low pressure is slightly small, and the power (a value obtained by multiplying driving torque by rotational speed, hereinafter referred to as a fan driving force) at the time when the fan is driven at the same rotational speed is high, so that the fan static pressure efficiency (a value obtained by multiplying static pressure by air flow and dividing by fan driving force) is decreased.
SUMMARY OF THE INVENTION
An object of the present invention is to reduce noise and to improve the energy efficiency of blower.
The blower and the method for determining a slit shape in accordance with the present invention realize reduced noise and improved energy efficiency of blower by properly setting the width and the number of the slits in a blower in which the slits are formed in an annular wall and air is sucked into the inner peripheral portion of the annular wall through the slits as a fan rotates.
According to the present invention, the efficiency of the blower can be enhanced, and a decrease in consumed energy and an increase in cooling capacity of an equipment can be realized.
The blower in accordance with the present invention is a blower in which an annular wall is spaced from the blade tip end of a fan, a slit for communication between the inner and outer peripheral portions of the annular wall is formed at a portion opposed to the blade tip end of the annular wall, and air is sucked to the inner peripheral portion of annular wall through the slits as the fan rotates. The width and the number of slits are so set that an air flow of 20 to 40% of the maximum air flow is sucked through the slits in a state in which the static pressure is zero.
Also, the blower in accordance with the present invention is characterized in that in the case where the width of the slit does not change in the radial direction, when the viscosity of air is taken as &eegr;, the inside diameter of annular wall as D, the radial-directional length of slit as L, the width of slit as a constant value of w, the number of slits as n, the maximum static pressure of blower as P
max
, and the maximum air flow of blower as Q
max
, the width and the number of slits are so set that the relationship between these particulars satisfies the following condition:
4.0
≤
π
·
D
·
n
·
w
3
·
P
max
12
⁢
η
·
L
·
Q
max
≤
13.0
Further, the blower in accordance with the present invention is characterized in that in the case where the width of slit changes in the radial direction, when the viscosity of air is taken as &eegr;, the inside diameter of annular wall as D, the radial-directional length of slit as L, the width of slit at a distance 1 from the inner periphery of the slit as w(1), the number of slits as n, the maximum static pressure of blower as P
max
, and the maximum air flow of blower as Q
max
, the width and the number of slits are so set that the relationship between these particulars satisfies the following condition:
4.0
≤
π
·
D
·
n
·
P
max
12
⁢
η
·
Q
max
⁢
∫
0
L
⁢
1
w
⁡
(
l
)
3
⁢
ⅆ
l
≤
13.0
Still further, the method for determining a slit shape of a blower in accordance with the present invention is characterized in that, in the above-described blower, the shape of the slit is so determined that an air flow of 20 to 40% of the maximum air flow is sucked through the slits, so that the aforementioned equations describing the relationship between the particulars are satisfied.


REFERENCES:
patent: 5288203 (1994-02-01), Thomas
patent: 5292088 (1994-03-01), Lemont
patent: 5393197 (1995-02-01), Lemont et al.
patent: 5407324 (1995-04-01), Starnes, Jr. et al.
patent: 5707205 (1998-01-01), Otsuka

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