Motor blower and electric vacuum cleaner using same

Abstract

 A motor blower (1) includes an electric motor (4) having a rotating shaft (3), a centrifugal blower (2) having a plurality of blower blades (34) and attached to the rotating shaft (3) of the electric motor (4), and a diffuser (21) having a plurality of diffuser blades (25) each of which is positioned at an outer peripheral portion of the centrifugal blower (21) so as to be opposed to air outlet portions formed to a circumferential surface of the centrifugal blower (21). Each of the blower blades (34) has a front end portion (34b) which is formed to almost linearly incline from one end portion toward another end portion of the blower blade (34). Due to the above structure, the motor blower (2) and the electric vacuum cleaner using the motor blower (2) can suppress or reduce a generation of abnormal noise even under operational conditions of low airflow rate and high frequency region.

Description

Field of the Invention

[0001] The present invention relates to a motor blower (electric motor-driven blower or motor fan) having an improved blower blade shape and an electric vacuum cleaner using the motor blower.

Related Art

[0002] In general, an electric vacuum cleaner includes a motor blower and a dust collecting means both being accommodated in a vacuum cleaner body. The electric vacuum cleaner sucks dust accumulated on a surface to be swept together with air by sucking force of the electric motor blower, and the sucked air and the dust are separated at the dust collecting means. The separated dust is accumulated in the dust collecting means, and the clean air from which the dust is separated is then discharged outside the cleaner body.

[0003] The motor blower includes an electric motor and a blower member rotated by the electric motor. A centrifugal type blower is used as such blower member, and the motor blower is provided with a diffuser for uniformly regulating a flow of the air discharged from the centrifugal blower.

[0004] The motor blower used for the electric vacuum cleaner has been demanded to reduce noise for protecting user from undesired noise.

[0005] As one countermeasure for reducing the noise, there has been proposed a centrifugal blower 51, as shown in Fig. 11, in which a blower blade 52 is configured to have an outer diameter smaller than that of a blower plate 53. The centrifugal blower of this type is excellent in audibility under normal operating conditions. However, in comparison with conventional and general centrifugal blowers in which the blower blade has the same outer diameter as that of the blower plate, there has been posed a problem such that the proposed centrifugal blower 51 generates undesired noises in an operating conditions of low airflow rate and high frequency region.

[0006] For the purpose of suppressing the high-frequency noise generated by the centrifugal blower, there has been also proposed an electric motor blower provided with a diffuser which is inclined in an outer circumferential direction, for example, refer to a Patent Document 1 (Japanese Patent Application, Laid-open Publication No. 2002-115698).

SUMMARY OF THE INVENTION

[0007] The present invention has been made in consideration of the circumstances encountered in the prior art as mentioned above, and an object of the present invention is to provide a motor blower and an electric vacuum cleaner using the motor blower capable of suppressing or reducing a generation of abnormal noise even if the vacuum cleaner is operated under conditions of low airflow rate and high frequency region.

[0008] To achieve the above object, the present invention provides a motor blower which comprises: an electric motor having a rotating shaft; a centrifugal blower having a plurality of blower blades separately disposed between a pair of opposing plates, the centrifugal blower being attached to the rotating shaft of the electric motor; and a diffuser having a plurality of diffuser blades (diffuser vanes) each of which is positioned at outer peripheral portion of the centrifugal blower so as to oppose to air outlet portions formed to a circumferential surface of the centrifugal blower, wherein each of the blower blades has a tip end portion which is formed to almost linearly incline from one side end portion toward another side end portion of the blower blade.

[0009] In the above aspect, it may be desired that the blower blades are provided to a portion between a front side plate disposed on a side of an air inlet port and a rear side plate provided so as to oppose to the front side plate and having the same diameter as that of the front side plate, and the one side end portion of the front end portion of the blower blade is positioned at a portion deviated from the outer peripheral end of the front side plate to a side of an axis of the centrifugal blower, while another side end portion of the front end portion of the blower blade is positioned at a portion deviated from the one side end portion of the front side plate to a side of the axis of the centrifugal blower.

[0010] In another aspect of the present invention, there is also provided a n electric vacuum cleaner comprising a vacuum cleaner body and a motor blower accommodated in the vacuum cleaner body, the motor blower having a structure mentioned above.

[0011] According to the present invention, there can be provided a motor blower capable of suppressing or reducing a generation of abnormal noise during the operation thereof.

[0012] Furthermore, according to the present invention, there can be provided an electric vacuum cleaner provided with such a motor blower to thereby suppress or reduce the generation of abnormal noise even if the cleaner is operated under the conditions of low airflow rate and high frequency region.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In the accompanying drawings:

Fig. 1 is a side view, half in section, showing a structure of one embodiment of a motor blower according to the present invention;

Fig. 2A is a plan view schematically showing a structure of a diffuser used for the motor blower of the above embodiment according to the present invention, and Fig. 2B is a bottom view schematically showing a structure of the diffuser;

Fig. 3 is an illustrated perspective view schematically showing a structure of a centrifugal blower used for the motor blower according to the present invention;

Fig. 4 is a longitudinal sectional view schematically showing the structure of the centrifugal blower used for the motor blower;

Fig. 5 is a plan view schematically showing a blower blade of the centrifugal blower;

Fig. 6 is an illustrated perspective view showing an entire outer configuration of an electric vacuum cleaner according to another embodiment of the present invention;

Fig. 7 is a graph indicating results of noise evaluation test conducted by using the motor blower according to the present invention under a state where a low airflow rate is realized, and the graph shows a relationship between voltage and noise level;

Fig. 8 is a graph indicating results of noise evaluation test conducted by using the one embodiment of a motor blower according to the present invention under a state where the low airflow rate is realized, and the graph shows a relationship between frequency and noise value;

Fig. 9 is a graph indicating results of noise evaluation test conducted by using the one embodiment of a motor blower according to the present invention under a state where a maximum airflow rate is realized, and the graph shows a relationship between voltage and noise level.

Fig. 10 is a graph indicating results of noise evaluation test conducted by using the motor blower according to the present invention under a state where the maximum airflow rate is realized, and the graph shows a relationship between frequency and noise value; and

Fig. 11 is an illustrated longitudinal sectional view schematically showing a structure of a centrifugal blower used in a conventional motor blower.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0014] An embodiment of a motor blower according to the present invention will be described hereunder with reference to the accompanying drawings.

[0015] FIG. 1 is a side view, partially in section, showing a structure of a motor blower according to the present invention.

[0016] As shown in FIG. 1, the motor blower 1 includes a centrifugal blower or fan 2 formed of metal, an electric motor 4 for rotating the centrifugal blower 2 through a rotating shaft 3, and a case 5 for accommodating the centrifugal blower 2 and the electric motor 4 together with associated members, if any.

[0017] The case 5 includes a blower cover 6 for covering the centrifugal blower 2, and a motor housing 7 for accommodating the electric motor 4.

[0018] As the electric motor 4, a brush-type motor is used. The motor housing 7 has a bottomed structure having a bottom portion formed by a rear plate 11, and the blower cover side of the motor housing 7 is opened as an opening 12 through which the electric motor 4 is accommodated in the motor housing 7.

[0019] A central portion of the rear plate 11 provided to a rear surface side of the motor housing 7 in an axial direction is protruded rearward in a shape of a cylinder so as to form a bearing-storage portion 12b in which a bearing 12a is accommodated.

[0020] A frame 8 is attached to the opening 12 of the motor housing 7 by means of screws 14 so as to be normal to the rotation shaft 3 of the motor 4.

[0021] The frame 8 has a bridge-shaped structure having a plurality of element extending radially from the rotation shaft 3 of the motor. An inner peripheral side lower end portion of the blower cover 6 is integrated with the motor housing 7 to thereby form the motor blower case 5.

[0022] Further, inner peripheral portions of the motor housing 7, the frame 8 and the blower cover 6 may be set so as to have the same dimension. The flame 8 is forwardly protruded at its almost central portion in a shape of cylinder so as to form a bearing-storage portion 13b having an opening as a through hole, not shown, through which the rotation shaft 3 penetrates. The bearing 13a is accommodated into the bearing-storage portion 13b.

[0023] The centrifugal blower 2 and the diffuser 21 are covered with the blower cover 6. The blower cover 6 is provided, at a central portion of a front surface thereof, with an inlet opening 6a opposing to an air-inlet port 31 of the centrifugal blower 2, while at an entire rear surface of the blower cover 6 is formed with a rear opening portion, not shown, so as to provide a substantially cylindrical shape in its entire configuration.

[0024] On the other hand, the motor 4 is composed of a stator 15 fixed to the motor housing and a rotor 16 provided inside of this stator 15. Both end portions of the rotation shaft 3 of the rotor 16 are rotatably supported by bearings 12a and 13a. A blowout nozzle, not shown, as an exhaust port, is opened at a peripheral surface close to the rear surface of the motor housing 7 directed in a radial direction.

[0025] Further, the diffuser 21 is fixed to a suction front side of the frame 8.

[0026] As shown in Fig. 2A, the diffuser 21 includes: a circular plate 22 having a substantially disc shape; a through hole 23 formed at a center of the circular plate 22 through which the rotation shaft 3 penetrates; screw holes 24a and 24b for inserting screws to fix the diffuser 21 to the frame 8; a plurality of circular-arc-shaped blades 25 provided in a vertical direction at a portion close to an outer peripheral portion of the diffuser 21 so that the plurality of blades 25 are positioned at an outer peripheral portion of the blower 2; and a plurality of circular-arc-shaped blades 26 provided in a vertical direction at a rear surface of the circular plate 22, each of the plurality of blades 26 are formed in a spiral shape.

[0027] Further, the diffuser 21 is inserted into an outer peripheral portion of the bearing storage portion 13b formed to the frame 8 so as to oppose to the frame 8, and the diffuser 21 is then fixed to the frame 8 by the means of screws.

[0028] As shown in Fig. 3 to Fig. 5, the centrifugal blower 2 includes a front side plate 32 provided to a side of an air inlet portion 31, and a plurality of blower blades 34. The blower blades 34 are provided to a portion between the front side plate 32 on the air suction port 31 side and a rear side plate 33 having the same diameter as that of the front side plate 32 and disposed so as to oppose thereto.

[0029] The blower blade 34 is provided with a plurality of mount projections 34a. The mount projections 34a are inserted into the mount holes 32a and 33a, and then the mount projections 34a are caulked. As a result, each of the blower blades 34 is fixed in a state that the blower blade 34 is sandwiched between the front side plate 32 and the rear side plate 33.

[0030] The air inlet port 31 is formed at a central portion of the front side plate 32, while an air outlet port 35 is formed at a portion between the and outer peripheral end portions 32b and 33b of the front side plate 32 and the rear side plate 33.

[0031] In a front end portion 34b of the blower blade 34, one side end portion 34b1 is positioned at an inner side (blower axial center side) of an outer peripheral edge portion 32b of the front side plate 32, while the other side end portion 34b2 is positioned at an inner side of an outer peripheral edge portion 33b of the rear side plate 33. That is, the front end portion 34b of the blower blade 34 is linearly inclined from one side end portion 34b 1 to the other side end portion 34b2 so that the other side end portion 34b2 is positioned at a portion deviated from one side end portion 34b1 to the blower axial center side.

[0032] Accordingly, as shown in Fig. 4, assuming that a diameter of the front side plate 32 is d1, a diameter of the rear side plate 33 is d2, a diameter of a circle on which the one side end portion 34b 1 is positioned is d3, and a diameter of a circle on which the other side end portion 34b2 is positioned is d4, the following relations will be established.

[0033] In this connection, the shape of the front end portion 34b of the blower blade 34 is not limited to a straight-line shape as disclosed in the present embodiment. There can be also adopted other shapes such as a curved-line shape, a shape combined a curved-line shape with a straight-line shape, a shape combined a straight-line shape with another straight-line shape as far as the combined shape constitutes an almost linear line shape.

[0034] In the motor blower 1 as constructed above, when the rotation shaft 3 is rotated, the centrifugal blower 2 is also rotated to thereby suck the air. The sucked air passes from the air inlet opening 6a formed to a front surface side of the blower cover 6, and blown out from the air outlet portion 35 through the centrifugal blower 2. Then, the air passes through portions between the circular-arc shaped blades 25 along an inner peripheral surface of the blower cover 6 and flows so as to spread in an axial direction. Further, in a rear surface of the circular plate portion 22, this air passes through portions between the circular-arc- shaped blades 26 toward the center of the diffuser 21 in an eddy current shape.

[0035] Thereafter, the air blown out from the air outlet port 35 of the centrifugal blower 2 is uniformly rectified and then introduced to the motor 4 by the diffuser 21. After the air introduced to the motor 4 cools the motor 4, the air is discharged outside of the motor housing 7.

[0036] According to results of the noise evaluation test conducted by the inventors of the subject application, a noise level of the motor blower of this embodiment can be lowered in comparison with that of the conventional motor blower in which an outer diameter of the blower blade is set to the same as that of the blower plate, and an operation of the motor blower of this embodiment can be performed in a calm and quiet manner.

[0037] Further, even if a voltage is varied for changing the rotation number, the noise level of the motor blower of this embodiment can be lowered in comparison with that of the conventional motor blower in which the outer diameter of the blower blade is set to the same as that of the blower plate, and the operation of the motor blower of this embodiment can be also performed in a calm and quiet manner.

[0038] Furthermore, since the front end portion 34b of the blower blade 34 is formed so as to linearly incline from the one side end portion 34b 1 to the other side end portion 34b2, there can be provided a motor blower capable of reducing a generation of abnormal noise even under operational conditions of low airflow rate and high frequency region, whereby the motor blower can be manufactured at a low cost with excellent mass- productivity.

[0039] According to the motor blower of the present embodiment, it becomes possible to suppress or reduce generation of abnormal noise even if the cleaner is operated under the conditions of the low airflow rate and the high frequency region.

[0040] As shown in Fig. 6, the motor blower 1 of the present invention is assembled into a cleaner body 42 of a vacuum cleaner 41. A windward side of the motor blower 1 is provided with a dust collecting means 43 including a centrifugal type dust collecting portion 43a and a pleat-shaped dust collecting filter 43b. A hose 44, an extension pipe 45 and a nozzle 46 are connected to the windward side of the dust collecting means 43 assembled in the cleaner body 42.

[0041] The vacuum cleaner 41 into which the motor blower 1 is assembled can suppress or reduce a generation of abnormal noise even under operational conditions of the low airflow rate and the high frequency region, i.e., even if a cross sectional area of an air flow path is narrowed due to the dust accumulated in the dust collecting means 43, the vacuum cleaner 41 can be operated in a calm and quiet manner. Further, the vacuum cleaner 41 can be calmly operated with a low noise level even if an voltage is changed.

[0042] According to the vacuum cleaner of the present invention, a generation of abnormal noise can be suppressed or reduced even if the cleaner is operated under conditions of the low airflow rate and the high frequency region.

[Exemplary Embodiment]

[0043] Noise levels at times of the low airflow rate and the maximum airflow rate were measured by using the motor blower (Example) according to the present invention such as shown in Fig. 1. The measured values were compared with those of the conventional motor blower (Comparative Example) such as shown in Fig. 11.

(1) Noise Evaluation Testing Conditions

[0044] 

1) Airflow Rate: low airflow rate (vacuum degree: large), and maximum airflow rate state (vacuum degree: small).

2) Measuring Method: in a state where the low airflow rate was realized, the motor is disposed on urethane so that a carbon brush of the motor is directed horizontally, while in a state where the maximum airflow rate was realized, the motor was set on a wrapper tube so that the carbon brush of the motor is directed horizontally.
A microphone for detecting the noise level was set to a position at a height of 1 meter from a center of an entire length of the motor. The low airflow rate was realized by controlling a valve opening angle of an airflow control valve so that the air flow rate Q was set to 1.3 m³/min when an operation voltage was 100V. At a state of the valve opening angle being fixed, the noise measuring operation was performed.
A measuring of the vacuum degree was performed at a windward portion of the blower.

3) Measuring Environment: ambient temperature was 24°C, moisture content was 48%, and air pressure was 729 mmHg.

(2) Results

[0045] 1) The results obtained from the noise evaluation test conducted under the state where the low airflow rate was realized are shown in the following Table 1 and Fig. 7.

Table 1

	Voltage of 40 [V]					Voltage of 60 [V]
Blower	Input [W]	Airflow rate [m3/min]	Vacuum degree [kPa]	Rotation number [min-1]	Noise value [dB(A)]	Input [W]	Airflow rate [m3/min]	Vacuum degree [kPa]	Rotation number [min-1]	Noise value [dB(A)]
Example	230	0.76	8.16	23600	83.1	440	0.99	13.95	31400	89.5
Comparative Example					83.4					91.8

	Voltage of 80 [V]					Voltage of 100 [V]
Blower	Input [W]	Airflow rate [m3/min]	Vacuum degree [kPa]	Rotation number [min-1]	Noise value [dB(A)]	Input [W]	Airflow rate [m3/min]	Vacuum degree [kPa]	Rotation number [min-1]	Noise value [dB(A)]
Example	730	1.16	19.81	38100	88.3	1070	1.30	25.63	44200	96.1
Comparative Example					90.8					94.5

As is clear from the results shown in Table 1, in a state where the low airflow rate (airflow rate Q=0.76 m³/min, voltage of 40V) is realized, the noise value of the motor blower of Example is 81.1 dB (A), while that of the motor blower of the Comparative Example is 83.4 dB (A).
When the voltage is 60V and the airflow rate Q is 0.99 m³/min, the noise value of the motor blower of Example is 89.5 dB (A), while that of the motor blower of Comparative Example is 91.8 dB (A).
Further, when the voltage is 80V and the airflow rate Q is 1.16 m³/min, the noise value of the motor blower of Example is 88.3 dB (A), while that of the motor blower of the Comparative Example is 90.8 dB (A).
Furthermore, when the voltage is 100V and the airflow rate Q is 1.3 m³/min, the noise value of the motor blower of Example is 96.1 dB (A), while that of the motor blower of the Comparative Example is 94.5 dB (A).
Accordingly, it can be confirmed that in a case where the low airflow rate (airflow rate Q=0.76 - 1.3 m³/min) is realized, the noise values of the motor blower of the Example are lower than those of the Comparative Example, and the motor blower of the Example can be silently operated with a low noise.
Further, as is evidenced from the results shown in Fig. 7, in a state where the low airflow rate is realized, it was confirmed that the noise values of the motor blower of the Example were clearly lower than those of the Comparative Example in an entire range of the voltage even if the voltage was varied for changing the rotation number of the blower.
Further, as shown in Fig. 8, as the result of measuring a mutual relation between a frequency of the noise and the noise level in a case where the low airflow rate at the voltage of 60V was realized, it was confirmed that the noise values of the motor blower of the Example were lower than those of the Comparative Example in an almost entire range of frequency.
In particular, in a frequency range exhibiting a peak having a frequency of 10KHz or higher, the noise values of the motor blower of the Example were evidently lower than those of the Comparative Example, so that it was confirmed that the suppression of the abnormal noise or the reduction of generating the abnormal noise could be effectively achieved.
2) The results obtained from the noise evaluation test conducted under the state where the maximum airflow rate was realized are shown in the following Table 2 and Fig. 9.

Table 2

	Voltage of 40 [V]					Voltage of 60 [V]
Blower	Input [W]	Airflow rate [m3/min]	Vacuum degree [kPa]	Rotation number [min-1]	Noise value [dB(A)]	Input [W]	Airflow rate [m3/min]	Vacuum degree [kPa]	Rotation number [min-1]	Noise value [dB(A)]
Example	260	1.68	0.60	21000	82.6	540	2.18	1.00	28000	87.6
Comparative Example					81.6					88.2

	Voltage of 80 [V]					Voltage of 100 [V]
Blower	Input [W]	Airflow rate [m3/min]	Vacuum degree [kPa]	Rotation number [min-1]	Noise value [dB(A)]	Input [W]	Airflow rate [m3/min]	Vacuum degree [kPa]	Rotation number [min-1]	Noise value [dB(A)]
Example	920	2.62	1.44	34300	89.6	1450	3.00	1.84	39900	82.0
Comparative Example					89.6					91.6

[0046] As is clear from the results shown in Table 2, in a state where the maximum airflow rate (airflow rate Q=1.68 m³/min, voltage of 40V) is realized, the noise value of the motor blower of the Example is 82.1 dB (A), while that of the motor blower of the Comparative Example is 81.6 dB (A).

[0047] When the voltage is 60V and the airflow rate Q is 2.18 m³/min, the noise value of the motor blower of the Example is 87.6 dB (A), while that of the motor blower of the Comparative Example is 88.2 dB (A).

[0048] Further, when the voltage is 80V and the airflow rate Q is 2.62 m³/min, the noise value of the motor blower of the Example is 89.6 dB (A), while that of the motor blower of the Comparative Example is 89.6 dB (A).

[0049] Furthermore, when the voltage is 100V and the airflow rate Q is 3.00 m³/min, the noise value of the motor blower of the Example is 92.0 dB (A), while that of the motor blower of the Comparative Example is 91.6 dB (A).

[0050] Accordingly, it can be confirmed that in a case where the maximum airflow rate (airflow rate Q=1.68 - 3.00 m³/min) is realized, there is no significant difference in noise level between the Example and the Comparative Example even if the voltage was varied for changing the rotation number of the blower.

[0051] Further, as is evidenced from the results shown in Fig. 9, it can be also confirmed that there is no significant difference in the noise level between the Example and the Comparative Example in an entire range of the voltage at the maximum airflow rate.

[0052] Furthermore, as shown in FIG. 10, as the result of measuring the mutual relation between the frequency of the noise and the noise level in a case where the maximum airflow rate at the voltage of 60V was realized, it was confirmed that there was no significant difference in the noise level between the Example and the Comparative Example in an entire range of the frequency.

[0053] It is to be noted that the present invention is not limited to the described embodiment and many other changes and modifications may be made without departing from the scopes of the appended claims.

Claims

1. A motor blower comprising:

an electric motor having a rotating shaft;

a centrifugal blower having a plurality of blower blades separately disposed between a pair of opposing plates, the centrifugal blower being attached to the rotating shaft of the electric motor; and

a diffuser having a plurality of diffuser blades each of which is positioned at an outer peripheral portion of the centrifugal blower so as to oppose to air outlet ports formed to a circumferential surface of the centrifugal blower,

wherein each of the blower blades has a front end portion which is formed to linearly incline from one side end portion of the blower blade toward another side end portion thereof.

2. The motor blower according to claim 1, wherein the blower blades are provided to a portion between a front side plate disposed on a side of an air inlet port and a rear side plate provided so as to oppose to the front side plate and having the same diameter as that of the front side plate, and the one side end portion of the front end portion of the blower blade is positioned at a portion deviated from the outer peripheral end of the front side plate to a side of an axis of the centrifugal blower, while another side end portion of the front end portion of the blower blade is positioned at a portion deviated from the one side end portion of the front side plate to a side of the axis of the centrifugal blower.

3. An electric vacuum cleaner comprising a vacuum cleaner body and a motor blower accommodated in the vacuum cleaner body, the motor blower comprising: an electric motor having a rotating shaft; a centrifugal blower having a plurality of blower blades, the centrifugal blower being attached to the rotating shaft of the electric motor; and a diffuser having a plurality of diffuser blades each of which is positioned at an outer peripheral portion of the centrifugal blower so as to oppose to air outlet ports formed to a circumferential surface of the centrifugal blower, wherein each of the blower blades has a front end portion which is formed to linearly incline from one side end portion of the blower blade toward another side end portion thereof.

Drawing