JP3647781B2 - Thin electric fan - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thin electric fan used for forcibly cooling an electronic element such as a CPU, a computer-related electronic device, or the like, or as an aspirator for equalizing the temperature in the device.
[0002]
[Prior art]
While recent electronic devices are becoming higher in density and smaller in size, the power consumption tends to increase, and the amount of heat generation increases accordingly. And if a large number of parts are arranged in a device with a certain space in a high density, it is not possible to expect sufficient heat dissipation due to the internal natural convection. The resulting electric fan has become indispensable.
[0003]
For example, a CPU in a personal computer has increased in calorific value with the recent high performance, and generally an electric fan is mounted on a CPU package to cool the CPU.
[0004]
As such an electric fan, a DC motor of a non-commutator using a magnet (permanent magnet) as a rotor is often used, and an air flow fan or a centrifugal fan is provided on the rotor itself. It is composed. In such an electric fan, as disclosed in Japanese Utility Model Publication No. 64-30654, etc., a pair of ball bearings is usually used to rotatably support the rotating shaft of the rotor. In addition, a preload is applied to each ball bearing by a coil spring.
[0005]
[Problems to be solved by the invention]
As described above, in recent electronic devices, the miniaturization of the whole and the increase in the density and performance of parts are progressing. Therefore, as a matter of course, a small and thin electric fan is desired. Yes. In particular, a CPU or the like in a so-called notebook personal computer requires a very thin electric fan.
[0006]
However, in the conventional configuration in which a pair of ball bearings is used for the bearing and a coil spring is provided for preloading the bearing, the axial dimension of the bearing portion is somewhat limited no matter how small each component is. There was a limit to the reduction in thickness of electric fans.
[0007]
If the preloading means such as a coil spring is omitted, vibration and wear are likely to occur due to slight imbalance of the rotor, cocking of the magnet, and running out of the lubricating oil film. Will be reduced.
[0008]
[Means for Solving the Problems]
The thin electric fan according to the present invention includes a non-commutator motor including a stator provided with a coil and an abduction type rotor provided with a cylindrical magnet, a blowing blade provided on an outer periphery of the rotor, and the fixed A thin electric fan comprising: a flat casing that supports a child on the bottom surface, and is surrounded by a wall portion on three sides and opened on one side as an air outlet. A rotating blade fixed at the center of the rotor is rotatably supported through one ball bearing provided on the casing side, and an end face of the cylindrical magnet is formed on the bottom of the casing. A magnetic plate opposite to this is disposed, and a preload is applied to the ball bearing by a magnetic attractive force generated between the magnetic plate and the cylindrical magnet.
[0009]
That is, the rotor that is rotatably supported via the ball bearing is attracted to the magnetic plate made of a magnetic material by the leakage magnetic flux from the cylindrical magnet, so that an appropriate preload is applied to the ball bearing. Since this magnetic plate can be arranged at a position that does not overlap with the ball bearing in the axial direction, there is no restriction on the axial dimension of the bearing portion, and in combination with a single ball bearing, the axial dimension. Is very short. Note that if one ball bearing is used, vibrations are more likely to occur due to rotor unbalance and magnet cocking than in the case of using two ball bearings. End up. In the present invention, even if there is only one ball bearing, by applying the preload, the swing of the rotating shaft is suppressed and smooth rotation is possible, and sufficient durability can be ensured.
[0010]
In the invention of claim 2, which further embodies the invention of claim 1, the magnetic poles of the stator and the magnetic poles of the cylindrical magnet are arranged to face each other in the radial direction. That is, the outer circumference of the stator is surrounded by a cylindrical magnet, and the magnetic poles on the outer circumference of the stator and the magnetic poles on the inner circumference of the rotor face each other.
[0011]
Here, when the magnetic center of the magnetic pole on the stator side and the magnetic center of the cylindrical magnet coincide with each other, an axial biasing force is generated between the stator and the cylindrical magnet. There is no. On the other hand, in the invention of claim 3, the magnetic center of the magnetic pole on the stator side and the magnetic center of the cylindrical magnet are shifted from each other in the direction in which the preload increases. That is, an axial biasing force is generated between the stator and the cylindrical magnet, and the preload applied to the ball bearing increases.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the thin electric fan of the present invention will be described in detail below with reference to the drawings.
[0017]
FIG. 1 is a plan view showing an embodiment of a thin electric fan according to the present invention, and FIG. 2 is a cross-sectional view taken along the line AA. The electric fan is used, for example, for cooling a CPU of a notebook personal computer, and has a substantially rectangular flat casing 1 that is attached to be overlaid on the upper surface of the CPU package. The commutator motor 2 is accommodated together with the blower blade 3.
[0018]
As shown in FIG. 2, the casing 1 is formed in a box shape having an open upper surface, and a cover 4 made of a thin metal plate is fixed so as to cover the opening. A circular air inlet 5 is formed in the cover 4 so as to correspond to the position of the blade 3. Moreover, as shown by a broken line in FIG. 1, the casing 1 has three side surfaces surrounded by walls, whereas one side surface is opened as an air outlet 6. The casing 1 is made of an aluminum alloy having excellent thermal conductivity, and itself functions as a heat sink for the CPU.
[0019]
A circular hole surrounded by a cylindrical boss portion 7 is provided at the substantially central bottom portion of the casing 1, and a cylindrical sleeve 8 is press-fitted and fixed therein. A stator 11 having a flat annular shape is fixed to the outer periphery of the upper portion of the sleeve 8. The stator 11 includes a coil 12 wound in a cylindrical shape, a pair of plate-like iron cores 13 provided on the upper end surface and the lower end surface of the coil 12, and an insulator disposed on the inner periphery of the coil 12. 14 and. As shown in FIG. 3, the iron core 13 has salient poles 13a at four locations in the circumferential direction, and a pair of upper and lower iron cores 13 are combined in a state of being shifted from each other by 45 °. That is, the salient pole 13a of the lower iron core 13 is positioned between two adjacent salient poles 13a of the upper iron core 13. As a result, the pair of iron cores 13 are alternately magnetized to the north and south poles with the commutation of the coil 12, and the whole stator 11 has N and S magnetic poles every 45 °.
[0020]
The end of the winding of the coil 12 is soldered to an annular coil board 15 made of a kind of printed wiring board located below the coil 12, and is provided on the bottom surface of the casing 1 through the coil board 15. Is connected to a circuit board 16 provided with the drive circuit. Reference numeral 17 in FIG. 2 indicates a soldered portion between the circuit board 16 and the coil board 15. A magnetic pole detection Hall element 18 is attached to one end of the circuit board 16. The Hall element 18 has a rectangular package, and the coil board 15 is provided with a rectangular cutout portion in order to avoid interference with the Hall element 18. The Hall element 18 slightly protrudes from the lower surface of the circuit board 16, but is accommodated in a recess formed on the bottom surface of the casing 1 correspondingly.
[0021]
A magnetic plate 21 described later is sandwiched between the coil board 15 and the iron core 13 on the lower surface of the stator 11 together with an annular spacer 22 made of synthetic resin.
[0022]
The rotor that constitutes the non-commutator motor 2 together with the stator 11 is substantially integrated with the blower blade 3 as a fan 31. That is, the fan 31 is made of a thin metal plate such as circular stainless steel, and is bent so that the outer peripheral portion thereof is lowered one step downward, and a large number of blowing blades 3 extending radially on the outer peripheral portion. Is formed.
[0023]
A cylindrical magnet 33 is fixed together with a magnet case 32 on the inner periphery of a cylindrical wall portion 31b formed between the central flat portion 31a and the blade 3. This cylindrical magnet 33 has a magnetic pole on its inner peripheral surface, and as shown in FIG. 4, N and S poles are alternately magnetized at 45 ° intervals. Needless to say, the number of magnetic poles of the cylindrical magnet 33 and the stator 11 is not limited to eight in the illustrated example. The magnet case 32 is made of a magnetic material and covers the outer peripheral surface of the cylindrical magnet 33.
[0024]
The cylindrical magnet 33 is disposed so as to surround the outer periphery of the stator 11, and the magnetic pole of the stator 11 and the magnetic pole of the cylindrical magnet 33 are disposed so as to face each other in the radial direction. In this embodiment, the magnetic center of the magnetic pole of the stator 11 (the axial height position in FIG. 2) coincides with the magnetic center of the cylindrical magnet 33. That is, the axial biasing force due to the magnetic center offset does not occur.
[0025]
A circular hole is opened at the center of the fan 31 and a cylindrical boss portion 31c is formed. A rotary shaft 34 is press-fitted and fixed to the inner periphery of the boss portion 31c. The rotating shaft 34 is rotatably supported via a single ball bearing 35 disposed in the sleeve 8 on the casing 1 side. This ball bearing 35 is formed of a shield ball bearing having shields on both sides, and a concave groove for receiving a steel ball is formed in each of the inner race 35a and the outer race 35b.
[0026]
The inner race 35a is a so-called clearance fit with respect to the rotating shaft 34, and the tip of the boss 31c of the fan 31 is in contact with the upper end surface of the inner race 35a. A snap ring 37 is attached to the concave groove at the tip of the rotating shaft 34 to prevent the rotating shaft 34 from falling off. Similarly, the outer race 35b has a clearance fit with the sleeve 8, and is fixed in the axial direction by a pair of upper and lower bearing stoppers 36 that are press-fitted and fixed in the sleeve 8.
[0027]
Therefore, the entire fan 31 as a rotor is rotatably supported by a ball bearing 35, and as is well known, a cylindrical shape is formed by the commutation of current to the coil 12 based on the magnetic pole detection of the Hall element 18. The fan 31 rotates in one direction together with the magnet 33.
[0028]
Here, the above-described magnetic plate 21 is provided at the bottom of the casing 1 so as to face the end face of the cylindrical magnet 33. The magnetic plate 21 is made of a magnetic material such as stainless steel or iron, and has an annular shape that fits on the outer periphery of the boss portion 7 of the casing 1 as shown in FIGS. As shown in FIG. 5, the magnetic plate 21 has a symmetrical shape having substantially rectangular cutout portions 38 at two positions separated by 180 °, and the Hall element 18 is disposed in one cutout portion 38 thereof. Has been. That is, the outer peripheral portion 21a of the magnetic plate 21 is at a radial position corresponding to the end surface of the cylindrical magnet 33. Similarly, the Hall element 18 is also at a radial position corresponding to the end surface of the cylindrical magnet 33. The hall element 18 is opposed to the end face of the cylindrical magnet 33 through 38. The outer peripheral portion 21a of the magnetic plate 21 is bent higher than the central portion so as to obtain an appropriate minute gap with the end surface of the cylindrical magnet 33.
[0029]
According to the configuration of this embodiment, a magnetic attractive force is generated between the cylindrical magnet 33 serving as the rotor and the magnetic plate 21, and the cylindrical magnet 33 and thus the entire fan 31 is attached toward the bottom of the casing 1. Be forced. As a result, a preload in the axial direction is applied to the ball bearing 35, and the swing of the rotating shaft 34 is prevented. Therefore, even with one ball bearing 35, it is possible to ensure a very smooth rotation without being affected by slight imbalance of the fan 31 or magnet cocking, etc., and also in terms of durability. It will be something. The magnetic plate 21 for applying the preload is disposed not on the central bearing portion but on the outer peripheral side of the ball bearing 35, so that the axial dimension of the bearing portion is not increased. Therefore, in combination with the single ball bearing 35, the entire electric fan can be made very thin. If specific dimensions are shown as an example, for example, an electric fan for a CPU can be configured to have a thickness of 5 mm or less.
[0030]
Further, in the above embodiment, by providing the notch 38 so as to avoid the Hall element 18, the magnetic pole detection of the Hall element 18 is not hindered at all, and both the Hall element 18 and the magnetic plate 21 are cylindrical. Since the magnet 33 can be disposed close to the magnet 33, an increase in thickness at this portion can be avoided. In addition, in the above configuration, by forming the notch portion 38 in a symmetrical position, the local loss of the magnetic attractive force can be balanced at two locations, and the occurrence of imbalance due to the formation of the notch portion 38 can be avoided. .
[0031]
In the above embodiment, as described above, the magnetic center of the magnetic pole of the stator 11 coincides with the magnetic center of the cylindrical magnet 33, and an axial biasing force is generated due to the offset of the magnetic center. However, if the magnetic center of the cylindrical magnet 33 is offset upward with respect to the magnetic center of the stator 11, an axial force is generated so that the cylindrical magnet 33 moves toward the bottom of the casing 1, and the ball It is possible to further increase the preload of the bearing 35.
[0032]
【The invention's effect】
As is apparent from the above description, according to the thin electric fan according to the present invention, it is possible to apply a preload to the ball bearing without using a means such as a coil spring that requires an axial space. Smooth rotation with little noise can be ensured. In addition, by using a blower blade formed of a thin metal plate such as stainless steel, the blower blade itself can be formed thinner than that made of a synthetic resin. Therefore, a single ball bearing can be used, and the electric fan can be configured to be very thin.
[0033]
Further, the preload can be further increased by shifting the magnetic center as in the third aspect.
[Brief description of the drawings]
FIG. 1 is a plan view showing an embodiment of a thin electric fan according to the present invention;
FIG. 2 is a cross-sectional view taken along line AA in FIG.
FIG. 3 is a plan view of the iron core,
FIG. 4 is a plan view of a cylindrical magnet,
FIG. 5 is a plan view of a magnetic plate,
FIG. 6 is a side view of a magnetic plate.
[Explanation of symbols]
1 Casing 2 Commutator Motor 3 Blower Blade
11 Stator
18 Hall element
21 Magnetic plate
31 fans
33 Cylindrical magnet
35 Ball bearing
38 Notch

Claims (3)

A non-commutator motor comprising a stator provided with a coil and an abduction type rotor provided with a cylindrical magnet, a blowing blade provided on the outer periphery of the rotor, and the stator supported on the bottom surface, A thin electric fan comprising a flat casing having a side wall surrounded by a wall and one side opening as an air outlet, and molding the blowing blade with a thin metal plate such as stainless steel, A rotating shaft fixed at the center of the rotor is rotatably supported through a single ball bearing provided on the casing side, and a magnetic plate facing the end face of the cylindrical magnet is disposed at the bottom of the casing. A thin electric fan, wherein a preload is applied to the ball bearing by a magnetic attractive force generated between the magnetic plate and the cylindrical magnet.   2. A thin electric fan according to claim 1, wherein the magnetic poles of the stator and the magnetic poles of the cylindrical magnet are arranged to face each other in the radial direction.   3. A thin electric fan according to claim 2, wherein the magnetic center of the magnetic pole on the stator side and the magnetic center of the cylindrical magnet are displaced from each other in the direction in which the preload increases.

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