JPH11150908A - Thin motor fan - Google Patents

Abstract

PROBLEM TO BE SOLVED: To materialize thinning of a motor fan, without being accompanied with degradation in durability, vibration deterioration, etc., of a ball bearing. SOLUTION: A brush-less motor 2 is composed of a stator 11 fixed to a casing 1, and a cylindrical magnet 33 on the side of a fan 31, and the magnet 33 surrounds the stator 11. The rotary shaft 34 of the fan 33 is supported rotatably by a single ball bearing 35 on the casing side. Since a magnetic plate 21 is arranged at the bottom of the casing 1 so as to confront the end face of the cylindrical magnet 33, magnetic attraction is generated between both, and axial pre-load is given to the ball bearing 35. The magnetic plate 21 is equipped with a cut for arranging a Hall element 18, and, to avoid the unbalance of attraction caused hereby, this fan is provided with a cut in a 180 deg. apart position, too.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forcibly cooling electronic devices such as a CPU and computer-related electronic devices.
Alternatively, the present invention relates to a thin electric fan used as an aspirator to equalize the temperature inside the device.

[0002]

2. Description of the Related Art In recent years, electronic equipment has been increasing in density and miniaturization, while power consumption has tended to increase, and the amount of heat generated has increased accordingly. If a large number of components are arranged at high density in a device in a certain space, the flow of airflow due to natural convection inside, that is, natural heat dissipation cannot be expected sufficiently, so the airflow in the device An electric fan that forces the flow of air is indispensable.

[0003] For example, the heat generation of CPUs in personal computers has increased with the recent increase in performance. Generally, an electric fan is mounted on a package of the CPU to cool it.

As such an electric fan, a non-commutator DC motor using a magnet (permanent magnet) for a rotor is widely used. An axial fan or a fan is provided on the rotor itself. It is configured as a centrifugal fan. In such an electric fan, a pair of ball bearings is generally used in order to rotatably support a rotating shaft of a rotor, as disclosed in Japanese Utility Model Application Laid-Open No. 64-30654. The configuration is such that a preload is applied to each ball bearing by a coil spring.

[0005]

As described above, in recent electronic equipment, the overall size has been reduced, and the density and performance of components have been increasing. However, a small and thin one is demanded. In particular, a CPU or the like in a so-called notebook personal computer requires a very thin electric fan.

However, in the conventional configuration in which a pair of ball bearings are used for bearings as described above and a coil spring is provided for applying a preload thereto, no matter how small each component is, the bearing portion is no longer used. The dimension in the axial direction becomes large to some extent, and there is a limit in making the electric fan thinner.

If the preload applying means such as a coil spring is omitted, vibration and wear are liable to occur due to slight imbalance of the rotor, cocking of the magnet, and breakage of the lubricating oil film. The durability is significantly reduced.

[0008]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a non-commutator motor comprising a stator having a coil and an external rotation type rotor having a cylindrical magnet, and provided on the outer periphery of the rotor. In a thin electric fan comprising a blowing blade and a casing supporting the stator, a rotating shaft fixed to the center of the rotor is rotated via one ball bearing provided on the casing side. A magnetic plate facing the end face of the cylindrical magnet is disposed at the bottom of the casing while freely supporting, and a preload is applied to the ball bearing by a magnetic attractive force generated between the magnetic plate and the cylindrical magnet. It is characterized by doing.

That is, since the rotor 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, an appropriate preload is applied to the ball bearing. . Since this magnetic plate can be disposed at a position where it does not overlap with the ball bearing in the axial direction, the axial dimension of the bearing portion is not restricted, and the axial dimension can be reduced in conjunction with the use of one ball bearing. Becomes very short. In addition, if one ball bearing is used, vibration is more likely to occur due to imbalance of the rotor and magnet cocking than in the case of two ball bearings. turn into. According to the present invention, even if only one ball bearing is provided, by applying a preload, the rotation of the rotating shaft is suppressed, and smooth rotation is possible, and sufficient durability can be secured.

[0010] In a second aspect of the present invention, the magnetic poles of the stator and the magnetic poles of the cylindrical magnet are radially opposed to each other. That is, the outer periphery of the stator is surrounded by a cylindrical magnet,
The magnetic poles on the outer periphery of the stator and the magnetic poles on the inner periphery of the rotor face each other.

If 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 due to the magnetic force is applied between the stator and the cylindrical magnet. It does not occur. 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 urging force is generated between the stator and the cylindrical magnet due to the magnetic force, and the preload applied to the ball bearing increases.

Further, in the invention according to claim 4, the magnetic plate includes:
It has an annular shape and has a notch in a part in the circumferential direction. In this notch, a Hall element for magnetic pole detection is arranged.

When a Hall element is used as a commutatorless motor to detect the magnetic pole of the rotor, this Hall element also needs to be arranged at a position to receive the leakage magnetic flux of the cylindrical magnet. In the configuration of the fourth aspect, the Hall element is disposed at a position facing the end face of the cylindrical magnet, and a predetermined preload is applied by a magnetic force between the magnetic plate and the cylindrical magnet in other portions. Therefore, the magnetic plate does not prevent the detection of the Hall element. The cutout may be a window-shaped opening.

Further, in the invention according to claim 5, the magnetic plate has a symmetrical shape having notches at two positions separated by 180 °, and the Hall element is arranged in one of the notches.

When a notch for a Hall element is provided in the magnetic plate, no attractive force is generated in this portion, and therefore, an unbalance of the attractive force occurs, which is not preferable. If the notches are provided symmetrically as in claim 5, imbalance in suction force is avoided.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a plan view showing one embodiment of a thin electric fan according to the present invention, and FIG. 2 is a sectional view taken along the line AA of FIG. This electric fan is used, for example, for cooling a CPU of a notebook personal computer, and has a substantially rectangular flat casing 1 which is mounted on the upper surface of a package of the CPU. The commutator motor 2 is housed together with the blow blade 3.

The casing 1 is formed in a box shape having an open top as shown in FIG. 2, and a cover 4 made of a thin metal plate is fixed so as to cover this opening. A circular air inlet 5 is formed in the cover 4 corresponding to the position of the blade 3. The casing 1 has three sides surrounded by walls as shown by broken lines in FIG. 1, while one side surface is open as an air outlet 6. The casing 1 is formed of an aluminum alloy having excellent heat transfer characteristics, and itself functions as a heat sink of the CPU.

A circular hole surrounded by a cylindrical boss 7 is provided at a substantially central bottom of the casing 1, and a cylindrical sleeve 8 is press-fitted and fixed therein. A flat annular stator 11 is fixed to the upper outer periphery of the sleeve 8. The stator 11 is disposed on a coil 12 wound in a cylindrical shape, a pair of plate-shaped iron cores 13 respectively disposed on an upper end surface and a lower end surface of the coil 12, and an inner periphery of the coil 12. And an insulator 14. 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 poles 13a of the lower iron core 13 are located between two adjacent salient poles 13a of the upper iron core 13. As a result, the pair of iron cores 13 are alternately magnetized into N poles and S poles with the commutation of the coil 12, so that the stator 11 as a whole has N and S magnetic poles every 45 °.

The ends of the windings of the coil 12 are soldered to an annular coil board 15 made of a kind of printed wiring board located below the coil 12, and a casing is connected via the coil board 15. It is connected to a circuit board 16 provided with a drive circuit disposed on one bottom surface. Reference numeral 17 in FIG. 2 indicates a soldered portion between the circuit board 16 and the coil board 15. A Hall element 18 for detecting a magnetic pole is attached to one end of the circuit board 16. This Hall element 18
Has a rectangular package, and the coil board 15 is provided with a rectangular notch in order to avoid interference with the Hall element 18. Note that this Hall element 18
Slightly protrudes from the lower surface of the circuit board 16,
Corresponding to this, the casing 1 is accommodated in a recess formed one step lower in the bottom surface.

Further, the coil board 15 and the stator 11
A magnetic plate 21 to be described later is sandwiched between the iron core 13 on the lower surface and an annular spacer 22 made of synthetic resin.

The rotor constituting the commutatorless motor 2 together with the stator 11 is substantially integrally formed as a fan 31 with the blowing blade 3. That is, the fan 31
Is formed of a thin metal plate such as a circular stainless steel, the outer peripheral portion of which is bent so as to be lowered one step downward, and a large number of blowing blades 3 extending radially are formed on the outer peripheral portion. I have. A cylindrical magnet 33 is fixed together with the magnet case 32 to the inner periphery of the cylindrical wall portion 31b generated between the central flat portion 31a and the blade 3. This cylindrical magnet 33 is
It has a magnetic pole on the inner peripheral surface, and as shown in FIG.
N poles and S poles are alternately magnetized at intervals of °. 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.

The cylindrical magnet 33 is disposed so as to surround the outer periphery of the stator 11,
One magnetic pole and the magnetic pole of the cylindrical magnet 33 are arranged to face each other in the radial direction. In this embodiment,
The magnetic center of the magnetic pole of the stator 11 (the height position in the axial direction in FIG. 2) coincides with the magnetic center of the cylindrical magnet 33. That is, no axial biasing force is generated due to the offset of the magnetic center.

In the center of the fan 31, a circular hole is opened and a cylindrical boss 31c is formed. A rotary shaft 34 is press-fitted and fixed to the inner periphery of the boss 31c. . The rotating shaft 34 is rotatably supported via a single ball bearing 35 disposed in the sleeve 8 on the casing 1 described above. The ball bearing 35 is formed of a shielded 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. The inner race 35a is a so-called clearance fit with respect to the rotation shaft 34, and the boss 31 of the fan 31
The end c is in contact with the upper end surface of the inner race 35a. In addition, 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.
The outer race 35b is similarly fitted with a gap with respect to the sleeve 8, and is fixed in the axial direction by a pair of upper and lower cylindrical bearing stoppers 36 which are press-fitted and fixed in the sleeve 8.

Therefore, the entire fan 31 serving as a rotor is rotatably supported by the above-described ball bearing 35. As is well known, the current is transferred to the coil 12 based on the detection of the magnetic pole of the Hall element 18. The flow causes the fan 31 to rotate in one direction together with the cylindrical magnet 33.

Here, the above-described magnetic plate 21 is disposed 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 around the boss 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 notches 38 at two positions separated by 180 °, and the Hall element 18 is disposed in one of the notches 38. Have been. That is, the outer peripheral portion 21a of the magnetic plate 21 is located at a radial position corresponding to the end surface of the cylindrical magnet 33, and similarly, the Hall element 18 is also located at a radial position corresponding to the end surface of the cylindrical magnet 33. The Hall element 18 faces the end face of the cylindrical magnet 33 through 38. The outer peripheral portion 21a of the magnetic plate 21 is bent one step higher than the central portion so as to obtain an appropriate minute gap with the end surface of the cylindrical magnet 33.

According to the configuration of this embodiment, magnetic attraction is generated between the cylindrical magnet 33 serving as a rotor and the magnetic plate 21, and the cylindrical magnet 33 and the fan 31 are generated.
The whole is urged toward the bottom of the casing 1. Thus, an axial preload is applied to the ball bearing 35,
Deflection of the rotating shaft 34 is prevented. Therefore, even with one ball bearing 35, a very smooth rotation can be ensured without being affected by a slight imbalance of the fan 31, magnet cocking, and the like, and the durability is sufficiently good. It becomes something. Since the magnetic plate 21 for applying the preload is arranged not on the center bearing but on the outer peripheral side of the ball bearing 35, the axial dimension of the bearing does not increase. Therefore, in combination with the single ball bearing 35, the entire electric fan can be made extremely thin. If specific dimensions are shown as an example, it is possible to configure the electric fan for a CPU to have a thickness of 5 mm or less, for example.

In the above embodiment, the notch 38 is provided so as to avoid the Hall element 18, so that the detection of the magnetic pole of the Hall element 18 is not hindered at all.
Since both the magnetic plate 8 and the magnetic plate 21 can be arranged close to the cylindrical magnet 33, an increase in the thickness at this portion can be avoided. Moreover, in the above-described configuration, by forming the notch 38 in a symmetrical shape, local loss of magnetic attraction can be balanced in two places,
Unbalance due to the formation of the notch 38 can be avoided.

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 such that the cylindrical magnet 33 moves toward the bottom of the casing 1, It is possible to further increase the preload of the ball bearing 35. In the above-described embodiment, the example in which the electric fan is configured as a centrifugal fan is described. However, the present invention is not limited to this, and it is of course possible to configure the electric fan as an axial fan.

[0030]

As is clear from the above description, according to the thin electric fan of the present invention, the preload is applied to the ball bearing without using a means requiring an axial space such as a coil spring. As a result, smooth rotation with little vibration and noise can be ensured. Therefore,
A single ball bearing can be used, and it can be made very thin.

The preload can be further increased by shifting the magnetic center as in claim 3.

Further, by providing a cutout in the magnetic plate as described in claim 4, it is possible to make the magnetic plate compatible with the Hall element for detecting the magnetic pole, and the magnetic pole detecting means does not become complicated or large. If the cutouts are paired as in claim 5, the imbalance of the magnetic attraction force due to the formation of the cutouts can be avoided.

[Brief description of the drawings]

FIG. 1 is a plan view showing one embodiment of a thin electric fan according to the present invention.

FIG. 2 is a sectional view taken along the line AA in FIG. 1;

FIG. 3 is a plan view of an 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 the magnetic plate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Casing 2 ... Commutatorless motor 3 ... Blower blade 11 ... Stator 18 ... Hall element 21 ... Magnetic plate 33 ... Cylindrical magnet 35 ... Ball bearing 38 ... Notch

Claims (5)

[Claims] 1. A non-commutator motor comprising a stator having a coil and an external rotation type rotor having a cylindrical magnet, a blower blade provided on an outer periphery of the rotor, and supporting the stator. And a rotatable shaft fixed to the center of the rotor is rotatably supported via one ball bearing provided on the casing side, and is provided at the bottom of the casing. A thin electric fan, comprising: a magnetic plate facing an end face of the cylindrical magnet; and a preload applied to the ball bearing by magnetic attraction generated between the magnetic plate and the cylindrical magnet. 2. The thin electric fan according to claim 1, wherein a magnetic pole of the stator and a magnetic pole of the cylindrical magnet are arranged to face each other in a radial direction. 3. The 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 shifted from each other in the direction in which the preload increases. 4. The magnetic plate has an annular shape,
The thin electric fan according to any one of claims 1 to 3, further comprising a notch in a part in the circumferential direction, wherein a Hall element for detecting a magnetic pole is arranged in the notch. 5. The magnetic plate according to claim 4, wherein the magnetic plate has a symmetrical shape having notches at two positions separated by 180 °, and the Hall element is arranged in one of the notches. Thin electric fan.