Pumps – Motor driven – Motor within rotary pumping member
Reexamination Certificate
2001-04-13
2003-02-11
Freay, Charles G. (Department: 3746)
Pumps
Motor driven
Motor within rotary pumping member
C417S423140, C417S423700, C415S119000
Reexamination Certificate
active
06517326
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a blowing apparatus.
BACKGROUND OF THE INVENTION
In recent years, with downsizing and electronizing tendencies of equipment, electrical circuits are frequently equipped at high densities. With such tendencies, since exothermic densities of electronic equipment are also increased, a blowing apparatus for cooling the equipment is used.
As shown in
FIG. 3
, a conventional blowing apparatus comprises a permanent magnet motor
3
. The motor
3
includes a stator
1
having salient poles
1
a
including armature windings and a rotor
2
having permanent magnets
2
a
magnetized to a plurality of poles. The motor
3
drives a fan
4
having a plurality of blades
4
a
. A housing
5
is disposed around an outer periphery of the fan
4
. The motor and the housing are fixed by means of a plurality of spokes
6
.
However, when the stator core is worked, magnetic characteristics of the silent poles of the stator core differ due to deviation of working distortion or composition of the magnetic materials, and due to this distortion, even if the position of the silent poles of the stator and the magnetic poles of the rotor, and the conductive state are stable, a difference in generated torque is generated depending upon the silent poles. Such variation in torque generated by the distortion of the stator is caused the same times as the number of rotor poles with respect to the rotation of the rotor. This variation in torque acts as a vibration source and generates vibration and noise. Further, when the fan is rotated, vibrations are generated the same times as the number of fan blades per one rotation. Here, if the rotation frequency is defined as 1-degree, and the number of vibration of the variation per one rotation of the rotor is defined as order, if the same number of blades as the order or a submultiple of vibration generated due to the stator distortion or twice the number of blades are mounted, vibration generated by stator distortion and vibration generated by the rotation of blades coincide with each other, and there is a problem that the vibration is increased. Thereupon, in the conventional technique, the number of rotor poles is 4 and the number of fan blades is 6 and thus, the basic order of vibration is 12th-degree which is a minimum common multiple of 4 and 6.
Further, in the rotor portion, depending upon mechanical distortion of a rotor frame and permanent magnet, polarization distortion of the permanent magnet, deviation caused by assembling distortion of a shaft and a bearing, effective magnetic flux amount crossing the stator winding from the rotor permanent magnet differs. That is, since the generated torque is different depending upon magnetic poles, this is a cause of vibration which generates distortion of rotation. The vibration caused by the rotor distortion is generated the same times as the number of stator silent poles with respect to the rotor rotation. If the same number of blades as the order or a submultiple of vibration generated due to the rotor distortion or twice the number of blades are mounted, vibration generated by stator distortion and vibration generated by the rotation of blades coincide with each other, and there is a problem that the vibration is increased. Thereupon, in the conventional technique, the number of rotor poles is 4 and the number of fan blades is 6 and thus, the basic order of vibration is 12th-degree which is a minimum common multiple of 4 and 6.
Further, in the permanent magnet motor, magnetic flux generated from the permanent magnet crosses the stator core. Since the stator core has a shape of the silent pole, the magnetic resistance is varied by the rotational position of the rotor and thus, torque called cogging torque which is proportional to variation ratio of the magnetic resistance is generated in the rotor. The cogging torque is varied depending upon the positional relation between the silent pole of the stator core and the rotor magnetic pole, and variation is generated in the minimum common multiple of the number of stator silent poles and the number of rotor magnetic poles with respect to the rotor rotation, and this causes vibration of the motor. If the same number of blades as the order or a submultiple of vibration generated due to the rotor distortion or twice the number of blades are mounted, vibration generated by stator distortion and vibration generated by the rotation of blades coincide with each other, and there is a problem that the vibration is increased. Thereupon, in the conventional technique, the number of stator silent poles is 4, the number of rotor magnetic poles is 4 and the number of fan blades is 6, the basic order of the cogging torque is 4 th-degree which is a minimum common multiple of the number of stator silent poles and the number of rotor magnetic poles, and the basic order of vibration is 12th-degree which is a minimum common multiple of 4 and 6.
In the blowing apparatus, the motor to which the fan is mounted is fixed to the housing through the spokes. Vibration generated by the motor and the fan is transmitted to the spokes and the housing. Therefore, shapes of the spokes and housing largely effect the vibration of the blowing apparatus.
As a method for reducing the vibration of the blowing apparatus, there is a method to reduce the cogging torque which is a source of vibration, and to optimize the shapes of various members, but even if the vibration source of the motor and the fan is reduced, vibration of the entire blowing apparatus is not reduced depending upon the combination in some cases.
The present invention is for solving the conventional problem, and it is an object of the invention to provide a blowing apparatus having low noise and vibration.
SUMMARY OF THE INVENTION
To solve the above problem, the present invention proposes a blowing apparatus comprising a stator having a core including a M-number of salient poles, a rotor having permanent magnets having a P-number of magnetic poles rotatably disposed such as to be opposed to magnetic pole surfaces of the stator, a motor for rotating a fan having a N-number of blades, a polygonal housing having a Q-number of sides disposed around an outer periphery of the fan, and a R-number of spokes for fixing the housing and the motor. The minimum common multiple is increased by various combinations of the numbers.
With the above means, it is possible to increase the order of vibration, i.e., it is possible to reduce the energy of vibration and to suppress the vibration and noise of the blowing apparatus. When the above blowing apparatus is mounted in a apparatus. When the above blowing apparatus is mounted in a personal computer as electronic equipment for example, it is possible to reduce the noise of the electronic equipment.
To solve the above problem, the present invention provides a blowing apparatus comprising a stator having a core including a M-number of salient poles, a rotor having permanent magnets having a P-number of magnetic poles rotatably disposed such as to be opposed to magnetic pole surfaces of the stator, the stator and the rotor, in combination, forming a motor for rotating a fan having a N-number of blades, a polygonal housing having a Q-number of sides disposed around an outer periphery of the fan, and a R-number of spokes for fixing the housing and the motor, wherein mN≠nM is satisfied.
The present invention satisfies mN≠nP.
If a minimum common multiple of the number M of the stator salient poles and the number P of rotor magnetic poles is defined as A, the invention satisfies mN≠nA.
Further, the invention satisfies mQ≠nM.
Further, the invention satisfies mQ≠nP.
Further, the invention satisfies mQ≠nA.
Further, the invention satisfies mQ≠nN.
Further, the invention satisfies mR≠nM.
Further, the invention satisfies mR≠nP.
Further, the invention satisfies mR≠nA.
Further, the invention satisfies mR≠nN.
Further, the invention satisfies mR≠nQ.
The present invention provides electronic equipment incorporating the above blowing appar
Fujinaka Hiroyasu
Okada Yukihiro
Yokote Shizuka
Freay Charles G.
Lin Han L.
Matsushita Electric - Industrial Co., Ltd.
Parkhurst & Wendel L.L.P.
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