JP2001234927A - Small-sized motor for information device and rolling bearing for the small-sized motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized motor for an information device which is thin and excellent in quietness, and rolling bearing used for the motor. SOLUTION: Rotating portions 3, 8 of a fan motor are supported by one rolling bearing 4, and the radial geometric clearance of the bearing 4 in a state built in the motor is made to be not less than -2 μm and not more than 5 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small motor used for information equipment, and more particularly to an MP which is required to be thin.
A small motor for information equipment suitable for a fan motor for cooling a U (ultra small processing unit) or IC (integrated circuit), a spindle motor for a high-capacity and small recording medium, and a rolling bearing used for the small motor. About.

[0002]

2. Description of the Related Art As a small motor for information equipment which is required to be thin, there is, for example, an MPU cooling fan motor.
The structure of a conventional MPU cooling fan motor is, for example, shown in FIG.
As shown in FIG. 4, a frame 1 having an inner / outer double cylindrical structure in which an inner cylindrical wall 1a and an outer cylindrical wall 1b concentric with the inner cylindrical wall 1a are continuously formed by a bottom plate 1c and formed in an annular shape is provided. A cylindrical housing 2 is provided at the center. A rotating shaft 3 that constitutes a part of a rotating portion is rotatably supported on the shaft core portion of the housing 2 via two rolling bearings 4 and 5 that are spaced apart from each other in the axial direction. .

The rolling bearings 4 and 5 used for a small fan motor or the like are small and difficult to handle.
Generally, the bearing inner ring and the rotating shaft 3 are loosely fitted to each other so as to be easily incorporated into the motor. Housing 2
Is fixed to the inner diameter surface of the inner cylindrical wall 1a of the frame 1. The motor stator 6 is fixed to the outer diameter surface of the inner cylindrical wall 1a. A rotor magnet 7, which is circumferentially opposed to the outer peripheral surface of the motor stator 6 via a predetermined gap, is fixed to the outer peripheral surface of a rotor case 8, which is a deep dish-shaped cylindrical body. The rotor case 8 is fitted and fixed to one end of the rotating shaft 3 so as to be integrally rotatable. Fan blades 9 of the fan are fixed to the outer peripheral surface of the rotor case 8.

A preload is applied to the upper and lower rolling bearings 4 and 5 by a spring 50 attached to the housing 2 and a retaining ring 51 attached to the rotating shaft 3. As a result, a uniform load is applied to the two rolling bearings 4 and 5 which are combined in the back surface, and the rotating shaft 3 is supported by the two support points P1 and P2, so that vibration and abnormal noise of the fan motor are prevented. Depending on the installation posture of the motor, an axial load may be applied to the upper rolling bearing 5 by its own weight of rotating parts such as the rotor magnet 7, the rotor case 8, the blades 9, and the like. No axial load is applied to 4 due to the weight of the rotating parts 3 and 8 of the motor.

[0005]

With the recent miniaturization and thinning of information devices, MPs used for the information devices have been developed.
Smaller motors for information devices, such as U cooling fan motors, are also required to be smaller and thinner. However, in the case of an MPU cooling fan motor or the like, two bearings are used as bearings for supporting the rotating parts 3 and 8 of the motor, and the two bearings 4 and 5 are arranged at a predetermined interval in the thickness direction W of the motor. Therefore, there is a problem that the thinning of the motor is limited by the presence of the bearings 4 and 5.

Here, in order to reduce the thickness of a small motor for information equipment, when the conventional motor structure and bearing specifications are used and only one bearing is used and the preload by the preload spring 50 is not applied to the bearing, , The preload applied to the bearing is
The load is applied only by the weight of the rotating portion of the fan motor and / or the magnetic attraction acting between the motor stator 6 and the rotor magnet 7. It should be noted that whether the self-weight or the magnetic attraction acts depends on the installation posture of the fan motor (for example, whether the fan motor is installed horizontally or vertically). Conventionally, since the motor stator 6 and the rotor magnet 7 are not offset in the axial direction, the axial magnetic attraction force as a preload by the motor stator 6 and the rotor magnet 7 is not so large.

In any case, the preload due to the own weight of the rotating portion of the motor or the magnetic attraction force is applied to the preload spring 5.
0 is very small compared to the preload. With this small preload, a uniform load is unlikely to be applied to the inside of the bearing, and depending on the operating environment of the motor (for example, when a moment load is applied due to the gyro action of the fan or unbalance of the fan), the load is applied to the rolling elements inside the bearing. In some cases, the required load is lost, and the rolling element collides with the bearing ring, causing abnormal noise. Therefore, there arises a problem that the quietness required for the fan motor cannot be secured.

Further, assuming that a preload is applied by a preload spring 50 whose axis is oriented in the thickness direction W of the motor as in the prior art, the length of the preload spring 50 and the spring 50
The motor becomes thicker by the amount of the holding jig (retaining ring, etc.). The present invention has been made by paying attention to the above points, and even if it is thinner, the load loss of the rolling element in the rolling bearing does not occur or even if it occurs, the effect is extremely small, and there is no generation of abnormal noise. An object of the present invention is to provide a small-sized motor for information equipment which has a noise level that does not cause a problem in practical use, that is, is thin and excellent in quietness, and a rolling bearing used for the motor.

[0009]

According to one aspect of the present invention, there is provided a rolling bearing for supporting a rotating portion of a small motor for information equipment, wherein a radial geometric clearance of the rolling bearing is provided. Is set to −2 μm or more and 5 μm or less.

Next, according to a second aspect of the present invention, a rotating portion of a small motor for information equipment is supported by one rolling bearing, and a radial geometric clearance of the rolling bearing in a state of being incorporated in the motor is provided. An object of the present invention is to provide a small motor for information equipment characterized by having a thickness of -2 μm or more and 5 μm or less. Here, if the radial geometric gap is negative, a preloaded state is applied, and the generation of abnormal noise is suppressed. Therefore, when the radial geometric gap is set to a negative value, the viewpoint of noise suppression is considered. Therefore, the negative value may be any numerical value, but in consideration of the assemblability, the lower limit value is set to −2 μm in the present invention as the assemblable limit value.

Further, as will be described later, even if the radial geometric gap is positive, if the radial geometrical gap is as small as 5 μm or less, the generated abnormal noise is small, so the upper limit is set to 5 μm. Next, according to a third aspect of the present invention, the rolling bearing is assembled to the motor by fitting at least one of the inner ring and the outer ring of the rolling bearing with the interference with the configuration described in the second aspect. It is characterized by having.

According to a fourth aspect of the present invention, there is provided a small-sized motor for information equipment in which a rotating shaft of the rotating portion is fixed to an inner ring of a bearing. The rotating shaft is provided with fixing means for contacting the end face and applying a torque stronger than the bearing torque by the frictional force and positioning the rotating shaft in the axial direction.

Next, according to a fifth aspect of the present invention, a rotating portion of a small motor for information equipment is supported by one rolling bearing, and a radial geometric clearance of the rolling bearing in a state of being incorporated in the motor is provided. 0 μm and more than 5 μm
m or less, and a magnetic preload means for applying a preload of at least 5 to 10 times the mass of the rotating portion to the rolling bearing at least in the axial direction by a magnetic attraction force. It is intended to provide a small motor.

According to the present invention, the rotating portion is supported by only one rolling bearing, so that a small motor for information equipment such as a fan motor for MPU cooling can be further reduced in thickness. Further, in the rolling bearing for supporting the rotating part of the small motor for information equipment, the radial geometrical gap (true radial internal gap, theoretical radial internal gap) by itself or when incorporated in the small motor for information equipment is -2. Since it is set to be in the range of about 5 μm, the rotating shaft of the rotating portion supported by the bearing does not swing or is suppressed in the axial direction. As a result, even if a moment load is applied to the motor, the effect of the load loss of the rolling elements is small, and therefore, there is no generation of abnormal noise of the fan motor, or even if it is extremely faint, it is possible to produce a sound that is not practically problematic. (See Table 1).

That is, by setting the radial geometric clearance to 0 or less, a preload is applied, and the rotating part does not move in the axial direction, thereby eliminating generation of abnormal noise. Further, even if the radial geometric clearance is positive, 0 to 5 μm By setting the value as small as possible, the effect of the load loss of the rolling element is small, and the noise can be suppressed to a level that does not cause a practical problem. At this time, in the invention described in claim 3, by fitting the inner ring / outer ring of the rolling bearing to the rotating shaft or the like with a margin, even if the radial geometric clearance is set to 0 or less,
For example, it is possible to prevent generation of abnormal noise due to slippage between the inner ring and the rotating shaft.

According to the fourth aspect of the present invention, the radial geometric clearance is set to 0 or less by applying a friction force to the inner ring of the bearing by the fixing means attached to the rotating shaft to apply a torque larger than the bearing torque. Even so, generation of abnormal noise due to slippage between the bearing inner ring and the rotating shaft is prevented. According to the fifth aspect of the present invention, even if the radial geometric clearance is a positive value, a desired large preload can be applied without using a spring without contact. As the magnetic preload means, for example, there is a method in which the center of the magnetic force in the axial direction of the rotor magnet and the stator is slightly shifted and set.

The magnitude of the preload applied by the magnetic preload means is set to 5 to 10 times the mass of the rotating portion (rotor).
The reason for doubling is as follows. That is, depending on the installation posture of the motor, the own weight of the rotating part may not be a preload to the bearing (for example, when the motor is installed vertically or inverted, or when installed in a personal computer, the installation may not be possible). Depending on the method, the installation state of the internal motor is changed). For this reason, in any of the installed states, the load of the rolling element was released inside the bearing, and the appropriate preload load was confirmed to prevent the rolling element from colliding with the raceway surface and generating abnormal noise. 5 to 10 times the mass of the rotating part (rotor). For this reason, the mass is defined to be 5 to 10 times the mass of the rotating portion (rotor).

The above-mentioned confirmation is performed by changing the axial load applied to the bearing by the magnetic attraction force of the magnetic preload means to various values, and shaking the motor while rotating so as to confirm the occurrence of abnormal noise. It was done. As the motor, an MPU cooling fan motor was used.

[0019]

Next, a first embodiment of the present invention will be described with reference to the drawings. Note that members and the like similar to those in the above-described conventional example are denoted by the same reference numerals and described. The same applies to the following embodiments. Here, in the following embodiments, an MPU cooling fan motor will be described as an example of a small motor for information equipment, but the present invention can be similarly applied to other small motors for information equipment.

FIG. 1 is a cross-sectional view of the MPU cooling fan motor according to the present embodiment in a vertical installation (rotation axis horizontal). First, the configuration will be described with reference to FIG.
The frame 1 is formed in a double cylindrical structure with the concentrically arranged inner cylindrical wall 1a and outer cylindrical wall 1b continued by a bottom plate 1c. At the center of the frame 1, a cylindrical housing 2 is fixed to the inner diameter surface of the inner cylindrical wall 1 a of the frame 1, and rotates with respect to the axis of the housing 2 via one rolling bearing 4. The shaft 3 is rotatably supported. A motor stator 6 is fixed to an outer diameter surface of the inner cylindrical wall 1a of the frame 1. A rotor magnet 7 that is opposed to the outer peripheral surface of the motor stator 6 via a predetermined gap is fixed to a cylindrical inner diameter surface of a rotor case 8 which is a deep dish-shaped cylindrical body. The rotating shaft 3 is fitted to one end of the through hole of the portion and is integrally fixed. Further, fan blades 9 of the fan are attached to the cylindrical outer diameter surface of the rotor case 8.

In this embodiment, the rolling bearing 4
Is formed in a state before being incorporated into the motor, that is, such that the radial geometric clearance of the bearing 4 alone becomes −2 μm or more and 5 μm or less. The inner ring 4n fitted to the rotating shaft 3 is positioned by bringing the other end surface into contact with the protrusion 8a of the rotor case 8 and locking one end surface with the retaining ring 11. The outer ring 4g is mounted on the inner diameter surface of the housing 2, and is positioned with one end surface locked to a housing step 12 projecting from the inner diameter surface of the housing 2 and the other end surface released.

In the fan motor having the above configuration, the rotating shaft 3
Since only one rolling bearing 4 is used, the motor can be made thinner. Further, the bearing 4 is mounted on the fan motor in a state where the radial geometric clearance is −2 to 5 μm, that is, the clearance is negative (including 0; the same applies hereinafter) and a preload is applied, or even if it is a positive value, it is small. For example, even if the rotating shaft 3 of the fan motor rotates from the horizontal state while tilting and the moment load due to the gyro action is applied to the rolling bearing 4, there is no load loss of the rolling element 4t. The effect is small.
Therefore, generation of abnormal noise of the fan motor can be prevented, or the noise can be suppressed to an extremely faint sound that does not cause a problem in practical use.

Next, a second embodiment will be described with reference to the drawings. This embodiment is not only a bearing structure,
This is a method based on a combination with a motor. FIG. 2 is a partial cross-sectional view illustrating the MPU cooling fan motor according to the present embodiment. The basic configuration of the second embodiment is the same as that of the first embodiment.

However, in the first embodiment, the rolling bearing 4 has a radial geometrical clearance before being assembled of -2 to -2.
Although the 5 μm bearing 4 is used, in the present embodiment, the rolling bearing 4 having a normal radial geometric clearance having a radial geometric clearance larger than 5 μm before being assembled is used. Then, the inner ring 4n of the bearing 4 and the rotary shaft 3 are fitted with a margin. Reference numeral 20 denotes a fitting portion. As a result, the rolling bearing 4 incorporated in the motor
Is set so that the radial geometrical gap is set to −2 μm or more and 5 μm or less.

The outer ring 4g of the bearing 4 and the housing 2 are fitted with a margin. Alternatively, a configuration for performing both of them at the same time may be adopted. Since only one rolling bearing 4 is used for the fan motor, the thickness of the fan motor can be reduced. The rolling bearing 4 has a radial geometric clearance of −2 to 5 μm, which is negative (including 0; the same applies hereinafter) or slightly positive, and is fitted to the rotating shaft 3 by press-fitting with an interference. , Inner ring 4 of bearing 4
n and the rotating shaft 3 are relatively positioned and integrated with the rotor case 8.

In this case, when the radial geometric clearance is negative, a preload is applied to the rolling bearing 4 in advance, and even if the radial geometric clearance is positive, the rolling bearing 4 exists in the center of the bearing 4 because it is very small. supporting the rotation shaft 3 at one support point P _0. Further, due to the above-mentioned fitting, the rotating shaft 3 does not slip, and even if the rotating shaft 3 of the fan motor rotates while tilting and a moment load is applied by the gyro action, the load of the rolling element 5t is not released. Therefore, generation of abnormal noise can be prevented.

Further, as compared with the first embodiment, there is an advantage that the rolling bearing 4 having a normal radial geometric clearance can be used. Other configurations, operations, and effects are the same as those in the first embodiment. Here, as described above, a guideline of a required interference in a case where the inner ring 4n of the bearing 4 and the rotating shaft 3 are fitted with an interference may be obtained based on the following calculation method (see FIG. 12). .

Assuming that the surface pressure of the inner race 4n is P, the unit area is A, the friction coefficient is μ, and the radius of the inner race 4n (or the radius of the rotating shaft 3) is r, the torque Tp generated by the interference pressure is Tp. = Μ · P · A · r.

Here, the unit area is 1 m ² . If this torque Tp is sufficiently larger than the bearing torque Tbrg, the inner ring 4n and the rotating shaft 3 will not slip. next,
A third embodiment will be described with reference to the drawings. FIG.
FIG. 5 is an enlarged sectional view of a bearing portion of an MPU cooling fan motor according to a third embodiment of the present invention.

The basic configuration of this embodiment is the same as that of the above-described embodiment, except that it is positioned at one or both of the outer diameter surface of the outer ring 4g and the inner diameter surface of the inner ring 4n of the rolling bearing 4 at the center in the width direction. A different point is that a stealing groove 13 is provided. FIG. 3 illustrates a case where the slush grooves 13 are provided in both the inner and outer rings. By providing this squeeze groove 13,
The thickness of the raceway groove 4m portion is reduced,
The rigidity of the bearing ring provided with is reduced. The rolling bearing 4 configured as described above is configured such that the raceway provided with the recess groove 13 is
The fan motor housing 2 and the rotating shaft 3 are fitted and assembled by press fitting. Since the rigidity of the bearing ring provided with the sunk groove 13 is reduced, the radial geometric clearance of the rolling bearing 4 can be managed in a wide range.

Next, a fourth embodiment will be described with reference to the drawings. FIG. 4 shows M according to a fourth embodiment of the present invention.
It is sectional drawing of a fan motor for PU cooling. This embodiment is a method in which abnormal noise can be completely eliminated even if a bearing having a positive clearance is incorporated.

The basic configuration of this embodiment is the same as that of each of the above embodiments. However, a magnetic preload means is provided and a preload is applied by magnetic attraction. Also, the radial geometric clearance of the rolling bearing 4 is set to 0 to 5 μm in the assembled state.
You have set. That is, the stator 6 and the rotor magnet 7 have substantially the same width.
It is relatively eccentric in the axial direction by L. As a result, the center of the magnetic force is displaced by L in the axial direction (the thickness direction of the motor), so that an axial magnetic attractive force corresponding to the displacement L is generated between the rotor magnet 7 and the stator 6. As a result, the rolling bearing 4 has an arrow symbol f
Can be applied. This eccentricity constitutes a magnetic preload means.

By adjusting the amount of eccentricity L, the preload f due to the magnetic attraction force is adjusted to 5 to 10 times the own weight of the rotating parts 3, 8 (rotor). Here, if the eccentricity L is set too large in order to apply a high preload, electromagnetic noise is generated from the rotating motor, which causes a problem in terms of quietness. Therefore, the preload is applied to the rotating parts 3, 8
It is preferable to adjust the amount to 5 to 10 times the weight of the (rotor) and not to generate an electromagnetic sound or to be equal to or lower than an allowable electromagnetic sound level. That is, the eccentricity L
The lower limit of the preload by the magnetic attraction force is
8 (rotor), and the upper limit of the amount of eccentricity L is controlled so as not to generate electromagnetic noise or to be less than an allowable level of electromagnetic sound. preferable.

In the MPU fan motor configured as described above, the rotor case 8 and the like, which are rotating members, are supported by one bearing 4. Therefore, the thickness of the fan motor is greatly increased as compared with the case of being supported by two bearings 4. Can be thin. In addition, since a member such as a spring for applying a preload is not arranged beside the bearing 4 (in the thickness direction of the motor), the motor can be made thinner even if the preload is applied.

The rotating parts 3 and 8 are supported by one bearing 4, and the radial geometric clearance of the bearing 4 is a positive value. However, by applying a preload to the bearing 4 as described above,
Deflection of the axis of the rotating parts 3 and 8 can be reduced. In particular, it is possible to provide an MPU cooling fan motor with low power consumption and small space because of one bearing 4 while realizing a noise level equivalent to that of an MPU cooling fan motor that supports a rotating member with two bearings 4. Become.

Other structures, operations and effects are the same as those of the above embodiment. Next, a fifth embodiment will be described with reference to the drawings. FIG. 5 is a cross-sectional view of an MPU cooling fan motor according to a fifth embodiment of the present invention, which can be said to be a modification of the fourth embodiment. In this embodiment, the stator 6 and the rotor magnet 7 are assembled without eccentricity, and a columnar magnet 16 having a diameter substantially equal to the diameter of the rotating shaft 3 is fixed in the axial direction with respect to the end face of the rotating shaft 3. The cylindrical magnet 16 is fixedly supported on the housing 2 via a plate component 15 made of resin or the like, and at least a portion 3a of the rotating shaft 3 opposed to the cylindrical magnet 16. Is composed of a ferromagnetic material (such as iron), thereby forming magnetic preload means.

The cylindrical magnet 16 does not need to have a diameter substantially equal to the diameter of the rotating shaft 3, but is preferably arranged concentrically from the viewpoint of preventing run-out and the like. Also, the shape of the cylindrical magnet 16 does not necessarily have to be a cylindrical shape. By setting the clearance between the cylindrical magnet 16 and the rotary shaft 3 to be very small (however, not less than の of the axial clearance of the bearing 4), the rotary shaft 3 is attracted to the magnet and A preload is applied to the bearing 4 to which the inner ring 4n is fixed. If the axial clearance of the bearing 4 is set to less than １ ／, the possibility that the end face of the rotating shaft 3 and the cylindrical magnet 16 come into contact with each other by magnetic force increases.

In this case, the preload applied to the bearing 4 is adjusted by adjusting the magnitude of the magnetic force of the cylindrical magnet 16 and the clearance between the cylindrical magnet 16 and the rotating shaft 3. The axial preload by the suction force is set to 5 to 10 times the own weight of the rotating parts 3 and 8 (rotor). The configuration, operation, and effects are the same as in the above embodiment.

Here, in the present embodiment, the cylindrical magnet 16 constituting the magnetic preload means is opposed to the rotating shaft 3 in the axial direction. However, since the cylindrical magnet 16 can be made thinner, the conventional magnet can be made thinner. Thus, the motor can be made thinner as compared with the case where the preload is applied by the coil spring. In addition, since the preload is applied to the bearing 4 in a non-contact manner, the degree of freedom of the layout of the preload components is also increased from this point, and the adverse effect of the preload components on the thickness of the motor can be suppressed.

The magnetic preload means of the fourth embodiment may be used together. Next, a sixth embodiment of the present invention will be described with reference to the drawings. The present invention is a method for preventing a shaft and a bearing inner ring from slipping mainly when a bearing having a negative clearance is incorporated. FIG. 6 is a sectional view of a main part of an MPU cooling fan motor according to a sixth embodiment of the present invention.

In this embodiment, the inner ring 4n of one rolling bearing 4 whose radial geometric clearance is set in the range of −2 to 5 μm is inserted into the rotating shaft 3 with a loose fit. A cylindrical body 21 as a fixing means for positioning the rotating shaft 3 in the axial direction is further inserted into the rotating shaft 3, and fixed by being brought into contact with one end surface (lower end surface) of the inner ring 4n which has been inserted previously.

The attachment of the cylindrical body 21 to the rotating shaft 3 may be fixed by press-fitting or may be fixed by bonding. Further, the material of the cylindrical body 21 may be a metal material or a rubber material capable of increasing a frictional force, and an O-ring or the like can be suitably used. Further, the end surface of the cylindrical body 21 on the contact side with the end surface of the inner ring 4n or the end surface on the contact side of the inner ring 4n of the rolling bearing 4 with
The frictional force may be enhanced by roughening the mesh or the end surface by knurling.

In this embodiment, the fixing means 21 causes a frictional force to act on the end face of the inner ring 4n of the bearing 4 so that the torque T
By applying the torque Tf exceeding brg, generation of abnormal noise due to slippage between the inner ring 4n of the bearing 4 and the rotating shaft 3 can be prevented even if the radial geometric clearance is a negative value. Other configurations and operational effects are the same as those of the above embodiment.

When the outer race slides, the outer race 4g and the housing 2 may be fitted together with a margin. Here, a guide of the necessary force when the inner ring 4n of the bearing 4 mounted on the rotating shaft 3 is integrated with the rotating shaft 3 by tightening with a fixing means may be obtained based on the following calculation method (FIG. 13). reference).

Assuming that the effective diameter (center diameter) of the fixing means (the tubular body 21) is R, the tightening force is F, and the friction coefficient is μ, the torque Tf based on the frictional force generated by the tightening force is Tf = μ · F · R.

If this torque Tf is sufficiently larger than the bearing torque Tbrg, the inner ring 4n and the rotating shaft 3 do not slip. For example, in the case of the rolling bearing 4 of the model number 693, the bearing torque Tbr when one of the radial geometric gaps, which is the most difficult to assemble, has a size of -3 μm is used.
Since g is 0.79 × 10 ⁻⁶ N · m, the interference and tightening force of the fixing means 21 may be determined so as to have a larger torque.

Next, a seventh embodiment of the present invention will be described with reference to the drawings. FIG. 7 is a sectional view of a main part of an MPU cooling fan motor according to a seventh embodiment of the present invention. This embodiment can be said to be a modification of the sixth embodiment, and differs from the sixth embodiment in that the fixing means 21 is of a retaining ring type. That is, the mounting groove 22 is formed in the rotary shaft 3 in advance, and the rolling bearing 4 is connected to the rotary shaft 3.
After that, the fixing means 21 is mounted in the mounting groove 22 using a normal retaining ring mounting jig, and the inner ring 4n of the bearing 4 is mounted.
Is fixed to the rotating shaft 3.

In this case, the mounting position L of the fixing means 21 (that is, the position of the mounting groove) L is equal to or slightly shorter than the sum of the width B of the inner ring 4n of the bearing 4 and the width I of the center of the rotor case 8 (L .Ltoreq.B + I). By doing so, the tightening force between the inner ring 4n of the bearing 4 and the rotating shaft 3 can be made sufficiently large, and slipping between the two 3 and 4 can be prevented.
Generation of abnormal noise can be prevented. In the case of this retaining ring type fixing means 21 as well, a mesh or end surface roughening by knurling is performed on the surface that comes into contact with the end surface of the inner ring 4n or the end surface that comes into contact with the inner ring 4n itself of the rolling bearing 4 to increase the frictional force. You may. In the seventh embodiment, since the fixing means 21 can be easily attached and detached using a jig, there is an advantage that the rolling bearing 4 can be easily replaced as needed.

Next, an eighth embodiment of the present invention will be described with reference to the drawings. FIG. 8 is a sectional view of a main part of an MPU cooling fan motor according to an eighth embodiment of the present invention. In this embodiment, a female screw 21f is formed in the inner diameter portion of the cylindrical fixing means 21 to form a nut, while the rotating shaft 3
A male screw is formed at one end (lower end) of the bearing 4, and the nut-shaped fixing means 21 is screwed into the male screw to tighten the bearing 4.
The inner ring 4n is pressed against the projection 8a of the rotor case 8, and the rotating shaft 3, the inner ring 4n of the bearing 4, and the rotor case 8 are integrated.

The inner ring 4n of the bearing 4 is
The rotational shaft 3 is fixed in the axial direction by determining the relative position between the rotating shaft 3 and the rolling bearing 4 and applying a preload to the rolling bearing 4 by a negative radial geometric clearance or making the radial geometric clearance a slightly positive value. It is fixed almost immovably, and generation of abnormal noise due to slippage between the inner ring 4n of the bearing 4 and the rotating shaft 3 can be prevented. This embodiment also has an advantage that the fixing means 21 can be easily attached and detached and the rolling bearing 4 can be easily exchanged, as in the third embodiment.

Next, a ninth embodiment of the present invention will be described with reference to the drawings. FIG. 9 is a sectional view of an MPU cooling fan motor according to a ninth embodiment of the present invention. The fixing means 21 of this embodiment comprises a disk-shaped head and a cylindrical body 21d protruding in one direction from the center thereof. A male screw 21m is formed on the outer diameter of the body 21d to form a bolt. And one end (lower end) of the rotating shaft 3
It differs from the above embodiments in that a female screw 24 is formed on the side.

The bolt-shaped fixing means 21 is screwed into the female screw 24 and tightened, so that the bolt-shaped fixing means 21 is brought into pressure contact with the projection 8 a of the rotor case 8 to integrate the rotating shaft 3, the inner ring 4 n of the bearing 4, and the rotor case 8. The relative positioning between the inner ring 4n of the bearing 4 and the rotating shaft 3 is performed by the tightening force of the screw. Further, by setting the negative or slightly positive radial geometric clearance of −2 to 5 μm of the rolling bearing 4, the rotating shaft 3 is fixed or swings immovably in the axial direction, and the inner ring 4 n of the bearing 4 and the rotating shaft 3 can be prevented from generating abnormal noise due to slippage.

This embodiment also has the advantage that the fixing means 21 can be easily attached and detached and the rolling bearing 4 can be easily replaced. Next, a tenth embodiment of the present invention will be described with reference to the drawings. FIG. 10 is a sectional view of an MPU cooling fan motor according to a tenth embodiment of the present invention.

In this embodiment, instead of abutting one end surface of the inner ring 4n of the bearing 4 on the projection 8a of the rotor case 8, the diameter of the base 3k of the rotating shaft 3 is increased and the plane of the step is changed to the inner ring 4n. Abuts on one end surface. This is easier to manufacture than providing the rotor case 8 with a protrusion, and has the advantage that the rotating shaft 3 can be more firmly connected to the rotor case 8.

This structure of the rotating shaft 3 can be applied to all the embodiments. In addition, the sixth to the above using the fixing means 21
In each of the tenth embodiments, the rotating shaft 3 and the rolling bearing 4
May be used in combination with an inner ring 4n. The outer diameter of the fixing means 21 is preferably larger than the outer diameter of the inner ring 4n of the bearing 4 and smaller than the inner diameter of the outer ring of the bearing 4.

Here, since the radial geometric clearance of the rolling bearing 4 in each of the above embodiments is in the range of −2 to 5 μm, the radial geometric clearance between the rolling element and the bearing ring is set to a radial geometric clearance of a normal size. It is inevitable that the bearings rise above the rolling bearings 4. Rolling bearing 4 with high surface pressure
When a load due to the gyro moment of the fan motor is applied, the fluctuation of the PV value used for evaluating the life of the bearing 4 increases. Therefore, in order to suppress the fluctuation of the PV value, it is desirable that the raceway groove R ratio (outer ring groove radius / inner ring groove radius) of the rolling bearing 4 at this time be within a predetermined range. As a result of the study by the present inventors, the outer ring groove radius is 54% of the rolling element (ball) diameter, while the inner ring groove radius is 56 to 60 of the ball diameter.
%, It was found that the fluctuation of the inner ring 4nPV value was minimized. That is, the rolling bearing 4 incorporated in the fan motor of the present invention preferably has a groove R ratio of 54/56 to 60.

As the rolling bearing 4, a general deep groove ball bearing can be exemplified, but a four-point contact ball bearing may be used. The four-point contact ball bearing can be achieved by adopting, for example, a gothic arc groove or the like as the shape of the raceway groove. Due to its structure, the axial clearance of the four-point contact ball bearing is smaller than that of the deep groove ball bearing. Therefore, even with the same preload, the deflection of the rotating shaft 3 can be suppressed smaller than that of the deep groove ball bearing. For example, the preload to be applied can be set small.

A double-row angular contact ball bearing may be used as the rolling bearing 4. A double-row angular contact ball bearing generally has a preload inside when assembled, and since it is a double-row bearing, it can have a working point distance with a contact angle equivalent to that when two bearings are used. In addition, when a double-row angular contact ball bearing is used as the bearing 4, the bearing width is required for the double-row, so that compared with the case of using one single-row bearing, there is a limit in terms of thinning. However, since the bearing rigidity can be increased, it is effective in some applications.

The number of balls (the number of rolling elements) incorporated in the bearing 4 is not limited. However, by specifying the number of balls as five, the number of balls from which a load is lost is limited. That is, by specifying the number of balls incorporated in the bearing 4 to be five,
The load loss of the rolling element 4t may be suppressed more effectively. In addition, in all of the above embodiments, the respective configurations may be used in appropriate combination.

[0060]

(Example 1) Radial geometric clearance size of a fan motor in which one rolling bearing corresponding to model number 693 (outer diameter 8 mm, inner diameter 3 mm, width 4 mm, rolling element; diameter 2 mm, 5 pieces) is assembled. Using samples of various sizes, the relationship between the size of the radial geometric clearance of the bearing 4 and the generation of abnormal noise when a moment load was applied by the gyro action during rotation of the motor was examined.

Experimental Conditions The installation posture of the fan motor and the type and magnitude of the load applied to the bearing 4 at that time were set as follows. A: Fan motor horizontal posture (rotary shaft 3 is vertical, rotor case 8 is up) Axial load (own weight of rotating part + magnetic attraction force) = 0.2N B: Fan motor vertical posture (rotary shaft 3 is horizontal) Axial Load (magnetic attraction force) = 0.1 N and radial load (own weight of rotating part) = 0.1 N C: Fan motor horizontal reversing posture (rotating shaft 3 is vertical and rotor case 8 is down) Axial load (rotating part Own weight-magnetic attraction force) = 0 N Motor rotation speed: 5000 rpm The gyro moment when the motor was tilted during rotation was assumed to be 0.8 x ^10-3 Nm.

Radial geometric clearance of bearing 4 (μm):
There were eight types of 2, 0, 2, 4, 5, 6, 8, and 10. Table 1 shows the experimental results.

[0063]

[Table 1]

In Table 1, .largecircle. Indicates that no abnormal noise was generated, .DELTA. Indicates slight abnormal noise (to the extent that no practical problem occurred), and X indicates that large abnormal noise was generated. No noise was generated in bearings 4 having radial geometric clearances of 0 and -2 μm. From this result, irrespective of the installation posture of the fan motor, if the radial geometric clearance of the bearing 4 is 0 or negative and the load is always applied to the rolling elements inside the bearing 4, the gyro moment is applied. However, it is clear that no abnormal noise is generated in the motor.

The radial geometric clearance of the bearing 4 is 2 to 5 μm
For the above-mentioned ones, the generation of a faint noise that was not a problem in practical use was recognized. From this result, regardless of the installation position of the motor fan, if the radial geometrical clearance of the bearing 4 is within the range of 2 to 5 μm, even if a gyro moment is applied, the abnormal noise becomes a problem in practical use. It is clear that no occurrences occur.

The radial geometric clearance of the bearing 4 is 6 to 10 μm.
At m, a loud noise is generated and is not possible. The radial geometric clearance of the current fan motor bearing is about 7 to 9 for MC3. (Embodiment 2) When a load due to the gyro moment of the fan motor is applied to the rolling bearing 4 in a state where the radial geometric clearance is -2 to 5 μm and the surface pressure is high, the fluctuation of the PV value increases. Therefore, the radial geometric clearance is set to 0.0
P when using a rolling bearing 4 which is fixed at
The relationship between the fluctuation of the V value and the ratio of the raceway groove R of the rolling bearing 4 was calculated by simulation.

Sample bearing 4: Equivalent to model number 693 as in Example 1, 1 radial geometric clearance: 0.002 mm (constant) Fan motor installation posture: horizontal posture (rotary shaft 3 vertical, rotor case 8 up) Bearing 4 Load: Axial load (fan's own weight + magnetic attraction force) = 0.2 N Motor rotation speed: 5000 rpm Gyro moment when the motor is tilted during rotation:
0.8 × 10 ⁻³ N · m The ratio between the outer ring groove diameter and the ball diameter size and the ratio between the inner ring groove diameter and the ball diameter size of the above-mentioned rolling bearing 4 are set in the range of 54% to 60%, respectively. And sort them out as appropriate,
With respect to the nine types of sample bearings shown in Table 2, the fluctuation of the maximum PV value of the inner ring 4n at the position of each rolling element was simulated.

[0068]

[Table 2]

FIG. 11 shows the result. At the position of each rolling element, the variation in the PV value is smallest when the outer ring groove R dimension is 54% of the ball diameter dimension and the inner ring groove R dimension is 57 to 60% of the ball diameter dimension (that is, 54/57 to 54/57). 54/60)
It can be seen that by setting the groove R dimension, the fluctuation of the PV value can be suppressed, which is effective for the long-term acoustic life required for the fan motor.

[0070]

As described above, according to the present invention,
The radial geometric clearance of the rolling bearing when incorporated in the rolling bearing itself or a small motor for information equipment is -2 to 5
Since the diameter is in the range of μm, even if a moment load due to the gyro moment of the fan or the like is applied to the bearing, it is possible to provide a rolling bearing in which the influence of the loss of the load of the rolling element is small. Therefore, a small motor for information equipment with excellent quietness, such as a fan motor suitable for cooling MPU, IC, etc., which is thin and does not cause practical problems even if there is no abnormal noise is provided. it can.

Further, since only one rolling bearing supports the rotating part, a thin motor can be obtained.
Further, when the invention of claim 3 or 4 is adopted, the inner ring of the bearing or the like is assembled with a tightening margin, or the inner ring of the bearing is fixedly integrated with the rotating shaft by a fixing means, and the bearing (Tbrg) is used based on the torque (Tbrg) of the bearing itself. Because the torque (Tf) due to the frictional force between the inner ring and the fixing means is increased,
Even if the radial geometric clearance is zero or negative, there is no slippage between the inner ring of the bearing and the rotating shaft, and the generation of abnormal noise of the fan motor can be prevented. Can be provided.

Further, when the invention of claim 5 is adopted, a preload necessary for preventing generation of abnormal noise can be applied to the bearing without contact.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a fan motor according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a main part of a fan motor according to a second embodiment of the present invention.

FIG. 3 is a sectional view of a main part of a fan motor according to a third embodiment of the present invention.

FIG. 4 is a sectional view of a fan motor according to a fourth embodiment of the present invention.

FIG. 5 is a sectional view of a fan motor according to a fifth embodiment of the present invention.

FIG. 6 is a sectional view of a main part of a fan motor according to a sixth embodiment of the present invention.

FIG. 7 is a sectional view of a main part of a fan motor according to a seventh embodiment of the present invention.

FIG. 8 is a sectional view of a main part of a fan motor according to an eighth embodiment of the present invention.

FIG. 9 is a sectional view of a main part of a fan motor according to a ninth embodiment of the present invention.

FIG. 10 is a sectional view of a main part of a fan motor according to a tenth embodiment of the present invention.

FIG. 11 is a graph showing a result of simulating the effect of the ratio of the raceway groove diameter to the ball diameter of a rolling bearing having a negative bearing clearance on the variation in PV value.

FIG. 12 is a plan view of a main part for explaining use conditions according to a second embodiment.

FIG. 13 is a plan view of a main part for explaining use conditions according to the embodiments of FIGS. 6 to 10;

FIG. 14 is a sectional view of a conventional fan motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Frame 2 Housing 3 Rotating shaft 4 Rolling bearing 4n Inner ring 4g Outer ring 6 Motor stator 7 Rotor magnet 8 Rotor case 13 Sliding groove 16 Magnet 20 Fitting part 21 Fixing means

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3J012 AB04 AB06 AB07 BB01 CB10 EB14 FB10 GB10 HB02 3J017 AA01 AA02 DA02 DB03 DB07 3J101 AA02 AA32 AA42 AA52 AA62 BA80 FA01 FA53 GA24 5H605 AA05 BB05 BB10 EB10 EB10 EB10 EB10 EB10

Claims (5)

[Claims] 1. A rolling bearing for a fan motor, wherein the rolling bearing supports a rotating part of a small motor for information equipment, wherein a radial geometric clearance of the rolling bearing is set to be not less than -2 μm and not more than 5 μm. 2. A rotating part of a small motor for information equipment is supported by one rolling bearing, and a radial geometric clearance of the rolling bearing in a state of being incorporated in the motor is set to be not less than −2 μm and not more than 5 μm. Motor for information equipment. 3. The rolling bearing is assembled to a motor by fitting at least one of the inner and outer races of the rolling bearing with interference.
Small motor for information equipment described in. 4. A small motor for information equipment, wherein a rotating shaft of the rotating part is fixed to an inner ring of a bearing, wherein the rotating shaft is in contact with an axial end surface of the inner ring to apply a torque stronger than a bearing torque by a frictional force of the inner ring. 3. The small motor for information equipment according to claim 2, wherein a fixing means for positioning the shaft in the axial direction is provided on the rotating shaft. 5. A rotating part of a small motor for information equipment is supported by a single rolling bearing, and a radial geometric clearance of the rolling bearing in a state of being incorporated in the motor is set to be larger than 0 μm and not smaller than 5 μm. And a magnetic preload means for applying a preload of at least 5 times and not more than 10 times the mass of the rotating portion to the rolling bearing by magnetic attraction in at least an axial direction.