JP3532701B2 - Inner diameter groove porous body bearing mechanism and motor having the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-accuracy rotary motor that achieves low vibration, low noise, and low gogging (or low jitter) and its bearing mechanism. For example, the present invention relates to a small-sized spindle motor such as a CD-ROM, an HDD, or an MO that is required to have no shaft runout at high speed rotation.

[0002]

2. Description of the Related Art As disclosed in Japanese Utility Model Publication No. 47-36739, a method of forming a groove in the inner diameter portion of a bearing is such that a dense smooth surface of a convex portion and a rough surface of a concave portion are combined with the inner diameter portion to cause friction. Some are aimed at reducing loss and noise. Further, as described in Japanese Utility Model Laid-Open No. 61-101124, a high degree of rotation accuracy is achieved by forming a spiral groove in the inner diameter portion of the bearing and guiding the lubricant inward as the shaft rotates. In addition, the energy loss is reduced, and since the bearing is made of sintered metal, it is easy to process the groove shape and the cost is low. Furthermore, JP-A-62
No. 167921 and JP-A No. 62-167922.
Japanese Unexamined Patent Application Publication No. JP-A-2003-242242 discloses a bearing having a combination of three or more arc-shaped surfaces having a curvature larger than that of the arc-shaped surface centered on the shaft center on the inner peripheral surface of the bearing, and an inner-diameter surface of which the arc-shaped surface is flat.
It is described that the friction loss can be reduced because the contact with the shaft becomes a line contact. Further, the bearing described in Japanese Patent Laid-Open No. 5-115146 is a sintered oil-impregnated bearing having a plurality of substantially rectangular groove portions on the inner diameter surface, and has a simple structure to improve dynamic pressure function and low noise. Achieving low wear.

As described above, in the technologies disclosed above, the clearance for forming the bearing inner diameter groove and supporting the shaft is provided in each case against the increase in the fluid resistance of the fluid lubricant due to the reduction of the clearance and the increase of the rotation speed. It is intended to reduce the fluid resistance without increasing. Further, due to the dynamic pressure effect in the groove associated therewith, the bearing rigidity of the shaft support portion is increased, metal contact is prevented, and noise is reduced.

[0004]

The above-described technique of forming a groove in the inner diameter as a bearing is certainly effective in reducing friction loss, but vibration of the shaft and the bearing mechanism is generated due to the dynamic pressure effect that accompanies it. It also becomes a source. This is not preferable from the viewpoint of high precision rotation, and particularly at the time of high speed rotation, there are often serious troubles such as generation of noise and vibration in a frequency annoying area. Further, most of these bearing devices are used as motor bearings, and as a motor component, the relationship with the stator and rotor becomes important. As a functional problem, the number of magnetic poles magnetized in the magnet or the number of poles of the armature causes harmonically-related gogging (or jitter) based on the least common multiple of them, and the motor itself, media, or system. It becomes the source of vibration. When the vibration due to the number of magnet magnetic poles and the number of armature poles and the vibration due to the bearing inner diameter groove match in frequency, the vibration is amplified and a large noise is generated or the shaft vibration is increased. This will cause local wear.

[0005]

As a technical means for solving the above-mentioned problems, as a technical means for solving the above problems, a groove is formed in the inner diameter portion of the porous body bearing, and the number (C) of the grooves corresponds to the number (A) of magnetic poles of the motor magnet. and to the armature pole number (B), nA-C ≠ 0
And mB-C ≠ 0 (where n, m are natural numbers) co the relationship
This is achieved by an inner diameter groove porous body bearing mechanism for a motor having a groove number satisfying the above condition. Also, by arranging the center positions of the grooves at a random pitch with respect to the center of the bearing inner diameter, it is possible to configure an inner diameter groove porous body bearing mechanism for a motor that can disperse the vibration caused by the bearing mechanism in frequency. Therefore, low noise and low vibration can be achieved. Moreover, by simultaneously providing the above-mentioned both constitutional requirements, it is possible to achieve the objectives of ultra-low noise and ultra-low vibration by their synergistic effect. Further, the friction torque can be further reduced by providing a portion having a small inner diameter at least at two locations near both end surfaces of the inner diameter portion and forming a groove in that portion.

Further, by making the pore distribution of the groove portion coarser than that of the other inner diameter portion and making the pore distribution of the groove portion 5% to 40% in area percentage, the groove effect can be ensured and the groove effect can be ensured. The width is 0.1 to 1
When the depth is 5 mm and the depth is 5 to 100 μm, the effect as a groove can be further increased.

[0007]

[Function] With respect to the number of magnet magnetic poles (A) and the number of armature poles (B) of the motor, the number of grooves (C) in the inner diameter portion of the porous body
Is basically a prime number, it is possible to prevent amplification due to resonance with respect to vibrations of A and B, but the object can be achieved even with the following relationship. The relationship is n
It is represented by AC ≠ 0 and mB−C ≠ 0 (where n and m are natural numbers ). That is, the number of grooves is not a natural multiple of A or B. Also, nA + mB−C ≠ 0
The relationship may be, that is, the number of grooves that is not a common multiple of A and B. This requires that the number of grooves be such that A and B do not resonate. If these expressions are satisfied, amplification of vibration due to resonance is suppressed, and extremely low noise and stable rotation with low vibration can be obtained. In other words, the present invention excludes the case where nA-C = 0 and mB-C = 0 .

As yet another method, if the bearing grooves are formed at regular positions no matter how many,
Large vibrations of a certain frequency always occur during one rotation due to the number of them, but by forming the groove center at a position at an irregular angle with respect to the center of the bearing inner diameter (random pitching), It is possible to disperse into several small vibrations during one rotation, and it is possible to reduce noise and vibration even for the bearing mechanism and the motor in which the bearing mechanism is mounted. Furthermore, when the groove is formed in a part of the inner diameter portion of the bearing, the effect is almost achieved. If there are two or more contact parts near at least both ends in the bearing length direction (both end face directions), the shaft can be supported between them, and rather the sliding area can be made larger than sliding in all of the bearing length direction. Since the coaxiality can be increased by correcting only that portion, the dimensional accuracy is improved.

Further, the groove has its effect, that is, a friction reducing effect by increasing pseudo clearance, a dynamic pressure effect at the groove corner portion, and a partial pumping action at the groove portion peculiar to the porous body. What is partial pumping?
The oil pressure generated on the inner diameter surface other than the groove permeates into the bearing, and the groove immediately next to the oil leaks from the bearing due to the negative pressure condition accompanying the shaft rotation and the volume expansion of the oil due to the rotating sliding heat. The oil circulation action is to supply the oil to the inner diameter surface of the shaft support portion while generating dynamic pressure by the shaft rotation.

The distribution of pores in this groove is as follows:
Since the inner diameter sliding portion (portion other than the groove) holds the shaft with a fluid, it is desirable that the pore distribution be dense. This can be said from the viewpoint of the oil film rigidity and bearing rigidity of the dynamic pressure medium that is impregnated into the porous body such as oil, but if it is made too dense, it will cause an oil circulation action such as a pump action peculiar to the porous body. An appropriate value is selected to some extent because it causes trouble. On the other hand, the pore distribution in the groove portion is coarse due to the action of the oil circulation function as the oil supply portion with respect to the inner diameter sliding portion, and it is necessary to supply a large amount of oil to the inner diameter portion. The level of pore distribution in the groove is preferably 5 to 40% (area percentage). If it is less than 5%, the oil supply action cannot be sufficiently exerted, and if it exceeds 40%, there is a problem that the material becomes too rough and the pores of the inner diameter sliding portion become too rough. Furthermore, in order to achieve the effect of the groove, the groove has a width of 0.1 to 1 m.
It is necessary that m and depth be 5 to 100 μm. Although there is a manufacturing problem in the width, if the width is 0.1 mm or less, the effect as the groove as described above cannot be expected, and the width is 1 mm.
With the above, the area of the inner diameter surface supporting the shaft is small, and sufficient oil film rigidity and bearing rigidity cannot be obtained. Further, when the depth is 5 μm or less, the effect as a groove cannot be sufficiently achieved, while when it is 100 μm or more, the dynamic pressure effect and the partial pump effect cannot be expected.

The present invention is premised on a porous body, and the conditions for using such a bearing having a groove on its inner diameter surface include a condition of high speed rotation and low load. Under such conditions of use, the pumping action peculiar to the porous body is an effective action against a load in a certain direction, so an active pumping action cannot be expected for applications with a relatively low load.
Circulation of the impregnated oil is activated by the partial pumping action of the groove according to the present invention, and maintenance-free and longer life are achieved by the oil circulation action inherent to the porous body. Further, as the effectiveness for the dynamic pressure type bearing manufactured by the melting method, it is possible to form the shape of the groove inexpensively and easily in addition to the above-mentioned pump action.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION When forming a groove in the inner diameter portion of a bearing made of a porous body, where the number of magnetic poles of a motor magnet is A and the number of poles of an armature is B, the number C of grooves is Set the number of so as to satisfy both . nA-C ≠ 0 and mB-C ≠ 0 where n and m are natural numbers .

[0013]

FIG. 1 shows an embodiment of the present invention when it is constructed as an actual motor. In this embodiment, the number of magnetic poles A of the motor magnet 1 is 8, the number of poles B of the armature 2 having the coil 4 is 6, and the number C of the grooves 6 formed in the inner diameter portion 5 of the bearing 3 is 7. Is. This motor satisfies the relationship of nA + mB-C ≠ 0 or nA-C ≠ 0 or mB-C ≠ 0 (where n and m are natural numbers ), and has low vibration, low noise and low goggling (in the actual motor test). Or the effect of low jitter) could be achieved. Further, in a motor using a bearing having an inner diameter groove number that does not satisfy any of the relations of nA + mB-C ≠ 0, nA-C ≠ 0 and mB-C ≠ 0 (where n and m are natural numbers ), the least common multiple of each Vibration was amplified by the harmonic component and its gogging (or jitter) was large at each frequency, and vibration and noise were generated.

FIG. 2 shows the shape of the groove 6 in the inner diameter portion 5 of the bearing 3. 2A to 2C show the shape of the bearing 3 viewed from above. In (a), the number of grooves 6 is 5, and the cross-sectional shape of the groove (hereinafter referred to as “groove shape”) is triangular. In (b), the number of the grooves 6 is 11, and the grooves 6 are arranged at a random pitch. In addition,
The centering position is set to the bearing center in consideration of the dynamic pressure balance due to the oil film pressure generation. The groove shape is an elliptic curve. In (c), the number of grooves 6 is 3, and the groove shape is rectangular. The groove can be formed in any shape as long as it can basically achieve the dynamic pressure effect and the pumping effect. FIGS. 2D to 2F are vertical cross-sectional views of another bearing 3. In (d), the groove 6 is inclined and penetrates to each end surface of the inner diameter portion 5. (E) is an example in which the groove 6 is V-shaped, and (f) is an embodiment having the groove 6 parallel to the axial direction of the bearing 3. However, (f) shows the case where the groove 6 penetrates vertically in the inner diameter portion 5, the case where the groove 6 is interrupted, and the case where the groove 6 exists only in the surface of the inner diameter portion 5. Even in such a mode, any combination of modes can be used without departing from the scope of the present invention as long as the dynamic pressure effect and the pump function described above can be achieved. According to the experiments conducted by the present inventors, similar groove effects were obtained in the case of any of the shapes (a) to (f).

FIG. 3 shows an example in which two bearings, which are normally assembled in a housing case, are integrated by the bearing 3. It escapes at the central part so that it slides at both ends near the end face of the bearing, and inner diameter grooves are formed at the sliding parts at both ends. This bearing has about the same friction torque as the two bearings assembled, and this bearing has the effect of reducing the friction torque as compared with the integrated type in which the inner diameter in the length direction does not escape. Was done.

[0016]

According to the present invention, in the porous body bearing and the motor using the same, the friction loss and the shaft runout can be reduced by the simple method as described above, and the vibration caused by the bearing can be achieved. Further, by suppressing the generation of noise associated therewith in terms of frequency to prevent resonance, it is possible to achieve the effects such as low vibration, low noise, and low gogging (or low jitter), which have been difficult in the past.
That is, it is possible to provide an inexpensive and effective means for an application in which a motor is required to rotate with higher precision than before, and it is expected that the bearing will have a longer life.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view showing the structure of a motor according to an embodiment of the present invention.

2 (a) to (c) are plan views of an embodiment of the bearing of the present invention, and (d) to (f) are vertical cross-sectional views of other bearing embodiments.

FIG. 3 is a vertical sectional view of an embodiment of the bearing of the present invention.

[Explanation of symbols]

1 magnet 2 armature 3 bearings 4 coils 5 Inner diameter 5a Sliding inner diameter 5b Non-sliding inner diameter 6 groove

Front page continuation (72) Inventor Makoto Kondo 520 Minorita, Minato, Chiba Prefecture, Hitachi Powdered Metals Co., Ltd. (56) References JP-A-5-115146 (JP, A) JP-A-6-249235 (JP, A) JP 7-6336 (JP, A) JP 9-112560 (JP, A) Jitsuko Sho 47-36739 (JP, Y1) (58) Fields investigated (Int.Cl. ⁷ , DB name) ) H02K 5 / 167,5 / 24 F16C 17 / 02,33 / 10

Claims (6)

(57) [Claims] 1. A porous bearing has a groove in its inner diameter, and the number of grooves (C) is nA-C with respect to the number of magnetic poles (A) and the number of armature poles (B) of a motor magnet. ≠
0 and mB-C ≠ 0 (where n, m are natural numbers) the relationship
An inner diameter groove porous body bearing mechanism characterized in that the number of grooves satisfy both of them. Wherein the center position of the porous body bearings guru over blanking is,
2. The inner diameter groove porous body bearing mechanism according to claim 1, wherein the inner diameter groove porous body is arranged at a random pitch with respect to the center of the inner diameter of the bearing. 3. A pore distribution of the glue over blanking portion of the porous body bearings are, said the other a coarse than the inner diameter portion of, and pore distribution of the groove portion is from 5 to 40% by area percentage The inner diameter groove porous body bearing mechanism according to claim 1 or 2. 4. The inner diameter groove porous body bearing mechanism according to claim 3, wherein the groove has a width of 0.1 to 1 mm and a depth of 5 to 100 μm. 5. The inner diameter groove porous body according to any one of claims 1 to 4, characterized in that the inner diameter groove porous body bearing has an inner diameter groove at least at two locations in the vicinity of both end surfaces, which is small. Body bearing mechanism. 6. A motor comprising the inner diameter groove porous body bearing mechanism according to any one of claims 1 to 5.