U.S. patent application number 11/095503 was filed with the patent office on 2005-10-06 for fluid pump apparatus.
This patent application is currently assigned to DENSO CORPORATION. Invention is credited to Tsuzuki, Kunihiro, Uchida, Akikazu, Yokoyama, Shinichi.
Application Number | 20050220614 11/095503 |
Document ID | / |
Family ID | 35054467 |
Filed Date | 2005-10-06 |
United States Patent
Application |
20050220614 |
Kind Code |
A1 |
Tsuzuki, Kunihiro ; et
al. |
October 6, 2005 |
Fluid pump apparatus
Abstract
In an air supply pump, having an electric motor and a blower
driven by the electric motor, the blower has an impeller having
multiple blades for compressing and pumping out the air. A value
(F) obtained by a formula (F=N.times.S) is made to be higher than
the audible frequency band to the human beings, wherein "N" means
number of blades of the impeller, and "S" means a number of
rotation of the impeller for each second at a normal rotational
speed. (".times." is a symbol for a mathematical multiplication.)
The frequency (F=N.times.S) of fan noises at a primary peak appears
at higher frequencies out of the audible frequency band, so that
the noises audible to the human beings can be reduced.
Inventors: |
Tsuzuki, Kunihiro;
(Obu-city, JP) ; Yokoyama, Shinichi; (Gifu-city,
JP) ; Uchida, Akikazu; (Kariya-city, JP) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
901 NORTH GLEBE ROAD, 11TH FLOOR
ARLINGTON
VA
22203
US
|
Assignee: |
DENSO CORPORATION
Kariya-city
JP
|
Family ID: |
35054467 |
Appl. No.: |
11/095503 |
Filed: |
April 1, 2005 |
Current U.S.
Class: |
415/206 |
Current CPC
Class: |
F04D 23/008 20130101;
F04D 29/663 20130101; F04D 29/161 20130101 |
Class at
Publication: |
415/206 |
International
Class: |
F01D 005/10 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 2, 2004 |
JP |
2004-109909 |
Claims
What is claimed is:
1. A fluid pump apparatus comprising: an electric motor; a blower
operatively connected to and driven by the electric motor, wherein
the blower has a fluid flow chamber and an impeller rotatably
supported in the fluid flow chamber, and the impeller has multiple
blades, wherein a value "F" obtained by a formula of "F=N.times.S"
is made to be a higher value than an audible frequency band,
wherein "N" is a number of blades, and "S" is a rotational number
of the electric motor for each second at its normal rotational
speed. (".times." is a symbol of a mathematical
multiplication.)
2. A fluid pump apparatus according to claim 1, wherein fin pitch
angles of the respective blades are made to be equal to each
other.
3. A fluid pump apparatus according to claim 1, wherein the number
of the blades is made to be a prime number.
4. A fluid pump apparatus according to claim 1, wherein the blower
has a blower housing forming the fluid flow chamber therein, a
partitioning portion is formed in the fluid flow chamber between a
starting portion and an ending portion of the fluid flow, and a
volume decreasing means is formed in the partitioning portion
adjacent to the ending portion of the fluid flow chamber, so that
across sectional area of the fluid flow chamber is gradually
decreased at the ending portion in a rotational direction of the
impeller.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is based on Japanese Patent Application No.
2004-109909 filed on Apr. 2, 2004, the disclosure of which is
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] This invention relates to a fluid pump apparatus, which
compresses and pumps out fluid by rotation of an impeller having
multiple blades, and in particular to an air supply pump in which
fan noises can be reduced.
BACKGROUND OF THE INVENTION
[0003] The following technical features are known in the art to
reduce fan noises of an electrical air pump, for example, as
disclosed in Japanese Patent Publication No. H9-209997;
[0004] (1) pitch angles of respective blades are designed to be
non-uniform to each other, and
[0005] (2) positions of blades, which are formed on both sides of
an impeller, are designed to be displaced by a half pitch in a
rotational direction of the impeller, at a position at which a
modulation point is zero.
[0006] According to the above conventional technical features, fan
noises generated at the both sides of the impeller are interfered
with each other to reduce sonic energies and thereby the fan
noises.
[0007] According to the above conventional method, however,
multiple noise peaks are de-concentrated at low frequencies and the
noises of such low frequencies may be generated, whereas noise
peaks at high frequencies can be suppressed at a normal (constant)
rotational speed of the electrical air pump. As a result, the total
fan noises in the audible frequency band to human beings can not be
reduced.
SUMMARY OF THE INVENTION
[0008] The present invention is made in view of the above problems,
and it is an object of the present invention to provide a fluid
pump apparatus which reduces noises audible to the human beings to
a small amount, by moving peak frequency of the noises to a higher
value out of the audible frequency band.
[0009] According to a feature of the present invention, a value (F)
obtained by a calculation of a formula (F=N.times.S) is made to be
higher than the audible frequency band to the human beings, wherein
"N" means number of blades of an impeller of the fluid pump
apparatus, and "S" means a number of rotation of the impeller for
each second at a normal (constant) rotational speed. (".times." is
a symbol for a mathematical multiplication.)
[0010] The frequency (N.times.S) of fan noises at a primary peak,
according to the above feature, appears at higher frequencies out
of the audible frequency band, so that the noises audible to the
human beings can be reduced.
[0011] According to another feature of the present invention, fin
pitch angles of the respective blades are made to be equal to each
other.
[0012] The peak frequencies of the fan noises can be centralized on
one point (frequency) according to such feature, and the variation
of the peak frequency at the primary peak is avoided. As a result,
the frequency of the fan noises at the primary peak can be
completely moved to the higher frequency out of the audible
frequency band.
[0013] According to a further feature of the present invention, the
number of blades of the impeller is so made to be a prime number,
so that fan noises are prevented from appearing at other
frequencies than that of the primary peak. As a result, the fan
noises of 0.5 peak are prevented from generating in the audible
frequency band to the human beings. The peak frequencies of the fan
noises are prevented from de-concentrating and the peak frequency
of the fan noises are prevented from generating in audible
frequency band.
[0014] According to a still further feature of the present
invention, a blower is formed by a vortex flow type blower, which
has a vortex flow chamber and an impeller rotatably supported in
the vortex flow chamber. A volume decreasing means, such as a
groove or an inclined surface, is formed in a partitioning portion,
which is formed in the vortex flow chamber between a starting
portion and an ending portion of the fluid flow.
[0015] According to the volume decreasing means, a cross sectional
area of the vortex flow chamber is gradually decreased at the
ending portion of the vortex flow chamber in a rotational direction
of the impeller (blades), so that pressure variation of the fluid
is decreased when the blades come across the partitioning portion,
to thereby reduce the fan noise (wind noise). With this
arrangement, the fan noises can be reduced, in particular, when the
primary peak of the fan noises passes through the audible frequency
band during periods of starting and stopping the air pump.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The above and other objects, features and advantages of the
present invention will become more apparent from the following
detailed description made with reference to the accompanying
drawings. In the drawings:
[0017] FIG. 1 is a cross-sectional view of an air supply pump,
according to an embodiment of the present invention;
[0018] FIG. 2 is a partial side view of a blower housing of the air
supply pump shown in FIG. 1;
[0019] FIG. 3A is an enlarged partial front view of an impeller of
the air supply pump shown in FIG. 1;
[0020] FIG. 3B is a partial side view of the impeller shown in FIG.
3A;
[0021] FIG. 4 is a graph showing noise level according to the
present invention; and
[0022] FIG. 5 is a graph showing noise level according to the
conventional apparatus.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
First Embodiment
[0023] The present invention will be explained below with reference
to the embodiment, in which the present invention is applied to an
electrical air supply pump, as shown in FIGS. 1 to 3.
[0024] The air supply pump compresses air and pumps out the
compressed air. The air supply pump is used, for example, in a
secondary air supply system for an automotive engine, wherein the
air supply pump supplies the compressed air into an exhaust pipe of
the engine at an upstream side of a catalyst for purifying the
exhaust gas.
[0025] The air supply pump, which comprises a blower device having
a double-blade and vortex flow type impeller, is shown as an
example in the first embodiment.
[0026] The air supply pump, as shown in FIG. 1, comprises an
electric motor 1, the above mentioned blower device 2, and an air
duct portion 4 in which a filter 3 is arranged.
[0027] (Electric Motor)
[0028] The electric motor 1 of this embodiment is a DC motor, which
comprises a stator 7 having a cylindrical yoke 5 and multiple
permanent magnets 6 fixed to an inner peripheral surface of the
yoke 5, a rotor (armature) 8 arranged in the stator 7, a brush
assembly 12 arranged in a motor housing 11 and having multiple
brushes 10 which are in a sliding contact with a commutator 9
provided in the armature 8.
[0029] The armature 8 comprises a rotational shaft 13 rotatably
supported by the motor housing 11 and the stator 7, an armature
core 14 fixed to the shaft 13, an armature coil wound on the
armature core 14, and the commutator 9 electrically connected to
the armature coil.
[0030] The brush assembly 12 comprises multiple brushes 10 to be
brought into the sliding contact with the commutator 9, a brush
holder 15 movably holding the brushes 10 therein, multiple springs
16 for urging the brushes 10 toward the commutator 9, and a spacer
17 for firmly supporting the brush holder 15 in the motor
housing
[0031] (Blower Device)
[0032] The blower device 2 has an impeller 21 of a double-blade
vortex flow type, and a blower housing 22.
[0033] The impeller 21 is formed into a disc shape, wherein
multiple blades (fins) 21a are formed at an outer periphery and at
both sides of the disc-shaped impeller 21. A center portion of the
impeller 21 is connected to an end of the rotational shaft 13 of
the electric motor 1 by a connecting means 23, so that the impeller
21 can be rotated integrally with the rotational shaft 13.
[0034] The blower housing 22 comprises a first casing 25 fixed to
the motor housing 11 by means of screws 24, and a second casing 27
fixed to the first casing 25 by clips 26. A vortex flow chamber
(fluid flow chamber) 28 is formed in the blower housing 22, for
compressing the air by the rotation of the multiple blades 21a of
the impeller 21.
[0035] The vortex flow chamber 28 is formed into a C-shaped space
formed at the outer peripheral portion of the impeller 21 (along
the multiple blades formed at the outer periphery of the impeller),
so that the air flows along this vortex flow chamber.
[0036] As shown in FIG. 2, an air inlet port 31 is formed in the
first casing 25 of the blower housing 22, at a starting portion 28a
of the vortex flow chamber 28 (a portion at which the blades 21a
come into the vortex flow chamber in accordance with the rotation
of the impeller 21). The air inlet port 31 is communicated with a
downstream side of the air duct portion 4, as shown in FIG. 1.
[0037] An air outlet port 32 is formed in the blower housing 22 at
an ending portion 28b of the vortex flow chamber 28 (a portion at
which the blades 21a exit from the vortex flow chamber in
accordance with the rotation of the impeller), so that the
compressed air is discharged through the air outlet port 32.
[0038] (Operation of the Electrical Air Pump)
[0039] When the electric motor 1 is connected to a battery (not
shown) of a vehicle through a relay, the electric power is supplied
to the electric motor 1, and the shaft 13 and the impeller 21 are
rotated together.
[0040] When the impeller 21 is rotated, the multiple blades 21 are
circumferentially moved (rotated) so that the air in the vortex
flow chamber 28 is compressed, while the air is moved from the
starting portion 28a to the ending portion 28b. Since a negative
pressure is generated at the air inlet port 31, the air is guided
(sucked) from the air duct portion 4 through the air filter 3
toward the air inlet port 31. On the other hand, since a positive
pressure is generated at the air outlet port 32, the air compressed
in the vortex flow chamber 28 is discharged from the air outlet
port 32.
[0041] A rotational speed, at which the electric motor 1 is
normally operated, is called as "a normal rotational speed".
According to the embodiment, operational modes of the electric
motor 1 is either "ON state (supply of the electric power)" or "OFF
state (cut off of the electric power)". When the electric power is
supplied to the electric motor 1, and the rotational shaft 13 and
the impeller 21 are rotated in a stable condition (at a stable
constant speed), the rotational speed of the stable condition
corresponds to the "normal rotational speed".
[0042] (Characteristic Features of the Embodiment)
[0043] According to the electric motor 1 of the embodiment, a peak
frequency of fan noise is moved to a higher frequency side out of
an audible frequency band, so that a noise level audible to human
beings is reduced.
[0044] In the electrical air pump of the embodiment, the multiple
blades (fins) 21a are rotated in one direction and each of the
blades 21a gives flow velocity to the air. A partitioning portion
33 is formed in the blower housing 22 for partitioning the vortex
flow chamber 28 between the starting and ending portions 28a and
28b, as shown in FIG. 2. As a result,
[0045] (1) the pressure of the air is varied each time when the
compressed air is guided to the air outlet port 32 by the
respective blades 21a, and thereby pulsation noise is generated,
and
[0046] (2) a wind noise is generated each time when the respective
blades 21a are moved from the ending portion 28b to the
partitioning portion 33.
[0047] Since the above pulsation noise is generated by variation of
the air pressure, when the respective blades 21a come across the
air outlet port 32, the frequency of the pulsation noise mainly
depends on a cycle during which the blade 21a comes across the air
outlet port 32.
[0048] In a similar manner, the wind noise is generated by the
variation of the air pressure, when the respective blades 21a come
across the partitioning portion 33. The frequency of the wind noise
mainly depends on a cycle during which the blade 21a comes across
the partitioning portion 33.
[0049] As above, each of the pulsation noise and the wind noise is
such a noise, wherein a frequency of the noise depends on the cycle
during which the respective blades come across fixed portions (the
air outlet port 32 and the partitioning portion 33). A primary peak
of the fan noise (the pulsation noise and the wind noise) appears
at the cycle during which the blade 21a comes across the fixed
portions 32 and 33).
[0050] Namely, the primary peak of the fan noise appears at a
frequency F (Hz), calculated by a multiplication of N and S,
wherein N is a number of blades 21a, and S is a rotational number
of the electric motor for each second (rotation/sec).
[0051] In the electrical air pump according to the embodiment, the
cycle (frequency) during which the blade 21a comes across the fixed
portions 32 and 33 is designed at a higher value than the audible
frequency band when the electric motor 1 is operated at the "normal
rotational speed" (at which the electric motor 1 is stably rotated
at the constant speed with current supply).
[0052] Namely, the frequency F is made at a higher value than the
audible frequency band Fh (Hz) (N.times.S=F.gtoreq.Fh) to the human
beings, wherein
[0053] the frequency "F" is calculated by a formula
"F"="N".times."S",
[0054] "N" is the number of the blades 21a,
[0055] "S" is the rotational number of the electric motor 1 for
each second (rotation/sec), when the electric motor 1 is operated
at the "normal rotational speed", and
[0056] .times. is a symbol for multiplication.
[0057] The "audible frequency band" means a range of frequency
within which the ordinal human being can hear the noise, whereas
"the higher value than the audible frequency band" means a
frequency at which the ordinal human being can not hear the noise.
For example, the higher value is more than 20 kHz.
[0058] FIGS. 4 and 5 show the noise levels with respect to
different noise frequencies, wherein FIG. 4 is a graph of the
present invention and FIG. 5 is a graph of the conventional
apparatus. As understood from those graphs, the frequency of the
primary peak appears at a frequency (around 20.5 kHz) higher than
20 kHz, an upper limit of the audible frequency band, as shown in
FIG. 4. On the other hand, the frequencies of the primary and 0.5
peaks appear within the audible frequency band, as shown in FIG. 5,
respectively at the frequency of 13 kHz and 6.5 kHz. As is also
understood from FIG. 4, the frequency of 0.5 peak does not appear
in the present invention.
[0059] As a result, the fan noise (the pulsation noise and the wind
noise) audible to the human beings is reduced to a smaller
value.
[0060] As described above, the blades 21a are formed at the both
sides of the impeller 21. And the fan noise (the pulsation noise
and the wind noise) is generated at the both sides of the impeller
21.
[0061] The respective numbers of blades 21a of the both (front and
back) sides of the impeller 21 are designed to meet the formula
("N".times."S"="F".gtoreq."Fh"). In this embodiment, the number of
blades of the front side is made to be the same to that of the back
side, wherein the number is 79.
[0062] According to the embodiment, fin pitch angles between the
neighboring blades 21a on one side (e.g. the front side) are made
equal to each other over the entire periphery of the impeller 21,
as shown in FIG. 3A. This is also true on the other (back)
side.
[0063] Further, as shown in FIG. 3B, the position of the blades 21a
of one side (the front side) in the rotational direction is the
same to that of the other (back) side. However, the position of the
blades of one side can be displaced by a half pitch (at a point at
which modulation point is zero) from the blades of the other
side.
[0064] As a result, the peak frequencies of the fan noises can be
centralized to one point (frequency) of the primary peak, and the
frequency of the primary peak is not varied at the normal
(constant) rotational speed of the electric motor 1. And thereby,
the frequency of the primary peak can be completely moved to the
higher range out of the audible frequency band to the human
beings.
[0065] According to the embodiment, the number of the blades 21a of
the respective sides of the impeller is selected at a prime number,
for example at the prime number of 79.
[0066] In the embodiment, the frequency "F" calculated by
"N".times."S"(=79.times."S") is designed to be 20.5 kHz. Namely, in
the embodiment, the impeller 21 is so designed that the primary
peak of the fan noise appears at the frequency of 20.5 kHz.
[0067] As a result, the fan noises of a half (1/2) peak or a
one-fourth (1/4) peak can be also prevented from appearing in the
audible frequency band to the human beings. Namely, the
de-concentration of the noise peaks can be prevented and thereby
the noise peaks are prevented from appearing in the audible
frequency band.
[0068] As shown in FIG. 2, multiple (two)grooves 34 are formed in
the partitioning portion 33 of the blower housing 22 at a side
close to the ending portion 28b of the vortex flow chamber 28, so
that the volume of the vortex flow chamber 28 is gradually
decreased as the impeller 21 is rotated. In other words, a cross
sectional area of the grooves 34 is gradually decreased in a
rotational direction of the impeller 21. The grooves 34 are formed
in the both partitioning portions 33 respectively opposing to the
side of the impeller 21.
[0069] The number of grooves 34 shall not be limited to two, and
one or three, or any other number of grooves can be formed. The
groove or grooves can be further replaced by an inclined surface
formed on the partitioning portions 33, at such positions at which
the blades 21a and/or the outer periphery of the blades come across
the partitioning portions 33.
[0070] As a result, the pressure change to be generated when the
blades 21a come across the partitioning portions 33 can be
suppressed to a smaller amount, and thereby the wind noise can be
reduced.
[0071] Furthermore, when the fan noises of the primary peak pass
through the audible frequency band during periods of starting and
stopping the operation of the electrical air pump, the fan noises
can be likewise reduced.
[0072] The grooves and the inclined surface are collectively
referred to as "a volume decreasing means" in this
specification.
[0073] (Other Modifications)
[0074] In the above embodiment, the present invention is applied to
the electrical air pump which compresses and pumps out the air.
However, the present invention can be used in other pump devices
which compress and pump out gas other than the air, or which
compress and pump out a mixture of gas and liquid (in a steam
phase).
[0075] Furthermore, in the above embodiment, the double-blade
impeller is used. The present invention can be also applied to the
blower having a single-blade impeller, in which multiple blades are
formed on one side of the impeller.
[0076] The present invention can be further applied to a
centrifugal type blower or an axial flow type blower, other than
the vortex flow type blower.
* * * * *