JP2000350402A - Miniature motor for information apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the size of a miniature motor for an information apparatus. SOLUTION: A cylindrical housing 2 is placed on the center of a frame 1, and a stator 3 is fixed to the outer circumferential surface of the housing 2 in the circumferential direction. A shaft member 4 is placed coaxially on the inner circumferential side of the housing 2. The inner circumferential surface of the housing 2 is connected to the shaft member 4 with one roller bearing 5, to make the housing 2 and the shaft member 4 rotatably support each other relatively. The stator 3 and a rotor magnet 7 have approximately the same width and are assembled so as to be relatively shifted in an axial direction by a length L. With this constitution, as the center of a magnetic force is relatively shifted by a length L in the axial direction, an attractive force corresponding to the shift value L is generated between the magnet 7 and the stator 3 in the axial direction. As a result, a prepressure in the axial direction is applied to the bearing 5.

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.
U cooling fan motor, IC cooling fan motor, high capacity F
The present invention relates to a small motor for information equipment suitable for a DD spindle motor or the like.

[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. In the structure of a conventional MPU cooling fan motor, for example, as shown in FIG. 7, a cylindrical housing 2 is disposed at the center of a frame 1, and a stator 3 is fixed to an outer diameter surface of the housing 2. Further, the shaft member 4 is coaxially disposed on the inner diameter side of the housing 2, and the inner diameter surface of the housing 2 and the shaft member 4 are connected via two rolling bearings 5.
The two bearings 2 and 4 are supported by the two bearings 5 so as to be relatively rotatable relative to each other. Further, the rotor case 6 is integrally fixed to the shaft member 4, and the rotor case 6
The rotor magnet 7 radially facing the stator 3 is fixed concentrically to the inner diameter surface of the cylindrical portion 6a, and the blade member 8 is fixed to the outer diameter surface of the cylindrical portion 6a.

The two rolling bearings 5 are arranged at predetermined intervals in the axial direction of the shaft member 4, the outer diameter of the outer ring is fitted to the inner diameter of the housing 2, and the inner diameter of the inner ring is 4, and the outer races of the two bearings 5 are further urged in the axial direction by a coil spring 10 arranged coaxially with the shaft member 4, so that a preload is applied to the two bearings 5. The preload is configured so that a uniform load is applied to both bearings 5.

In FIG. 7, reference numeral 2a denotes a step provided on the housing 2, and reference numeral 9 denotes a snap ring for retaining.

[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 an MPU cooling fan motor or the like, two bearings 5 are used as bearings for supporting a rotating member of the motor, and since the two bearings 5 are arranged in the thickness direction W of the motor,
There is also a problem that the bearing 5 limits the thinning of the motor.

Here, in order to reduce the thickness of a small motor for information equipment, if the conventional motor structure and bearing specifications are used and only one bearing is used and no preload is applied to the bearing, the inside of the bearing is Equal load is not applied. In this case, depending on the usage environment of the motor, the load factor on the bearing fluctuates more than allowable, and the load on the rolling elements is lost, which causes abnormal noise from the motor.

Further, assuming that a preload is applied by a coil spring 10 whose axis is oriented in the thickness direction W of the motor as in the prior art, the motor becomes thicker by the length of the coil spring 10. SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a small motor for information equipment that can be further thinned.

[0008]

In order to solve the above-mentioned problems, a small motor for information equipment according to the present invention supports a rotating member of the motor with one rolling bearing and applies a preload to the bearing. It is characterized by having. By supporting the rotating member of the motor with one bearing,
Compared to a case where two bearings are arranged side by side in the thickness direction of the motor to support the rotating member, the thickness of the motor can be significantly reduced.

Further, by applying a predetermined preload to the bearing, generation of abnormal noise from the motor can be suppressed even if only one bearing is used. Means for applying the preload include a method of applying a preload to the bearing in a non-contact manner using the magnetic force of the magnet, such as slightly shifting the center of the magnetic force in the axial direction between the rotor magnet and the stator, and a method of applying the motor housing and the shaft member. On the other hand, it is conceivable that the inner and outer rings of the bearing are assembled with a certain amount of interference, or a preload is applied by making the internal clearance of the bearing negative. By employing such a preload applying means, the space for one bearing and the coil spring in the related art can be reduced, and the thickness can be further reduced.

It is preferable that the load factor ε of the rolling elements in the bearing be maintained at 40% or more with respect to the moment load generated by the centrifugal force due to the gyro action or unbalance of the fan. The load factor ε is
It can be adjusted by adjusting the preload. By setting the load factor ε to 40% or more, abnormal noise does not occur as a small motor for information equipment, and it is possible to achieve a noise level equal to or higher than that when two bearings are used.

Here, the load factor ε in the present specification is represented by the following equation. When the load factor ε is set to 40% or more, the number of rolling elements of the bearing is preferably set to five. 5 rolling elements
By specifying the number of rolling elements, even if the preload is small, the number of rolling elements that cause the bearing to lose load is reduced, and the load ratio ε is easily set to 40% or more. Generally, the number of rolling elements of the bearing used in the MPU cooling fan motor is six or more.

[0012]

Next, a first embodiment of the present invention will be described with reference to the drawings. Here, in this embodiment and the following embodiments, a small motor for information equipment is M
Although a PU cooling fan motor will be described as an example, the present invention can be similarly applied to other small motors for information equipment.

FIG. 1 is a diagram showing an MPU cooling fan motor according to the present embodiment. First, the configuration will be described. A cylindrical housing 2 is arranged at the center of a frame 1, and a stator 3 is fixed to an outer diameter surface of the housing 2 along a circumferential direction. A shaft member 4 is coaxially arranged on the inner diameter side of the housing 2, and the inner diameter surface of the housing 2 and the shaft member 4 are connected by one rolling bearing 5. The housing 2 and the shaft member 4 are supported by the one rolling bearing 5 so as to be relatively rotatable relative to each other.

The outer race of the rolling bearing 5 is fitted to the inner diameter surface of the housing 2 from the right side in the figure, and is positioned by abutting one end surface on a step 2a provided on the inner diameter surface of the housing 2. . The inner race of the rolling bearing 5 is fitted to the outer peripheral surface of the shaft member 4 from the left side in the figure, and is positioned by abutting on a rotor case 6 described later. Code 9
Represents a snap ring.

A rotor case 6 is integrally fixed to the shaft member 4, and a cylindrical portion 6a of the rotor case 6 is provided.
The inner diameter surface faces the stator 3 from the outer diameter direction, and the rotor magnet 7 is fixed to the inner diameter surface of the cylindrical portion 6a. Further, a blade member 8 is fixed to the outer diameter surface of the cylindrical portion 6a. The stator 3 and the rotor magnet 7 have substantially the same width.
It is assembled with only eccentricity. As a result, the center of the magnetic force is displaced by L in the axial direction (the thickness direction of the motor), whereby an axial attractive force corresponding to the displacement L is generated between the rotor magnet 7 and the stator 3. As a result, an axial preload is applied to the bearing 5. This eccentricity constitutes a preload applying means.

Then, by adjusting the amount of eccentricity L, the preload applied to the bearing 5 is adjusted, and the load factor ε of the bearing 5 is reduced by:
Set to 40% or more. If the amount of 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 amount of eccentricity L is such that the load factor ε on the bearing 5 is 40%.
It is necessary to adjust the amount so as not to generate the electromagnetic sound or to reduce the electromagnetic sound level to an allowable level or less. That is, the lower limit of the amount of eccentricity L is regulated by an amount such that the load ratio ε to the bearing 5 becomes 40% or more, and the upper limit of the amount of eccentricity L does not generate electromagnetic noise or the allowable amount of electromagnetic noise. It is regulated by keeping the amount below the level.

In the MPU fan motor having the above-described structure, the rotor case 6 and the like, which are rotating members, are supported by one bearing 5, so that the thickness of the fan motor is greatly increased as compared with the case where the bearing is supported by two bearings 5. Can be thin. Further, the motor can be made thinner because the preload applying means is not arranged beside the bearing 5 (in the thickness direction of the motor). In addition, the structure is such that the rotating members 4 and 6 are supported by a single bearing 5.
By applying a preload to the shaft, the runout of the axis of the rotating member can be suppressed to a small value.

In particular, by setting the load factor ε for the bearing 5 to 40% or more, the noise level equivalent to that of the MPU cooling fan motor in which the rotating member is supported by the two bearings 5 is realized, It is possible to provide an MPU cooling fan motor with low power consumption and a small space for each unit. here,
The number of balls (the number of rolling elements) incorporated in the bearing 5 is not limited. However, by specifying the number of the balls to be five, the number of balls to be unloaded is limited, and the preload is not increased so much. Can set a load factor of 40% or more. That is,
By specifying the number of spheres incorporated in the bearing 5 to be five, even if the eccentric amount L by the preload applying means is reduced,
A load factor of 0% or more can be achieved. Even if other preload applying means is adopted, it is easy to achieve a load factor of 40% or more by specifying the number of balls incorporated in the bearing 5 to be five.

Next, a second embodiment will be described with reference to the drawings. Note that the same reference numerals are given to the same components and the like as in the above embodiment, and the description thereof will be omitted. The basic configuration of the present invention is the same as that of the first embodiment, but the configuration of the preload applying means is different. That is, as shown in FIG. 2, the stator 3 and the rotor magnet 7 are assembled without eccentricity, and a cylindrical magnet 20 having a diameter substantially equal to the shaft diameter of the shaft member 4 is attached to the end face of the shaft member 4. It is arranged concentrically with a predetermined clearance in the axial direction, and its cylindrical magnet 20 is attached to a plate component 21 made of resin or the like.
And at least a portion 4 of the shaft member 4 which faces the cylindrical magnet 20
By configuring a with a ferromagnetic material (such as iron), a preload applying means is configured.

The cylindrical magnet 20 does not need to have a diameter substantially equal to the diameter of the shaft member 4, but is preferably arranged concentrically from the viewpoint of preventing run-out and the like. Further, the shape of the columnar magnet 20 does not necessarily have to be a columnar shape. By setting the clearance between the cylindrical magnet 20 and the shaft member 4 to be very small (however, １ ／ or more of the axial clearance of the bearing 5), the shaft member 4 is attracted to the magnet, and A preload is applied to the bearing 5 to which the inner ring is fixed. If the axial clearance of the bearing 5 is set to less than 1/2, there is a high possibility that the end face of the shaft member 4 and the cylindrical magnet 20 come into contact with each other by magnetic force.

In this case, by adjusting the magnitude of the magnetic force of the cylindrical magnet 20 and the clearance between the cylindrical magnet 20 and the shaft member 4, the preload applied to the bearing 5 is adjusted, and The load factor ε is set to 40% or more.
The configuration, operation, and effects are the same as in the above embodiment. Here, in the present embodiment, the cylindrical magnet 20 constituting the preload applying means faces the shaft member 4 in the axial direction. However, since the cylindrical magnet 20 can be made thin, a coil spring as in the related art is used. The motor can be made thinner than in the case of applying a preload. In addition, since the preload is applied to the bearing 5 in a non-contact manner, the degree of freedom of the layout of the preload components is increased from this point as well, and the adverse effect of the preload components on the motor thickness can be suppressed.

Incidentally, the preload applying means of the first embodiment may be used in combination. Next, a third embodiment will be described with reference to the drawings. Note that the same reference numerals are given to the same components and the like as in the above embodiment, and the description thereof will be omitted. In the present embodiment, as shown in FIG.
This is an example using the internal specifications of the bearing.

That is, when the bearing 5 is fitted and assembled to the housing 2 and the shaft member 4, the outer ring and the housing 2,
By making one or both of the inner ring and the shaft member 4 fit together with an interference, the radial clearance inside the bearing 5 is reduced (to a degree that does not cause a negative clearance) or is made a very small negative clearance. The load factor ε by 40%
Above.

This achieves a reduction in the sound level by suppressing the shaft center swing during the rotation of the fan, while realizing a reduction in thickness. In this case, the preload is in the radial direction. In the present embodiment, since the preload is applied by interference or the like, there is no need to arrange a preload component in the axial direction of the bearing, and even if the preload is applied to the bearing 5, the motor does not become thick.

At this time, the inner and outer rings 5b, 5
As shown in FIG. 4, a recess 22 (sludge) may be provided continuously or at a predetermined interval in the circumferential direction. It should be noted that the slack 22 may be only one of the inner and outer rings 5b and 5a. By forming the slack 22, the rigidity of the races 5 a and 5 b to be press-fitted is reduced, and the radial clearance can be adjusted over a wide range. Further, a preload applying means using a magnet as described above may be used in combination.

Other structures, operations and effects are the same as those of the above embodiment. Next, a fourth embodiment will be described with reference to the drawings. Note that the same reference numerals are given to the same components and the like as in the above embodiment, and the description thereof will be omitted. In the present embodiment, as shown in FIG. 5, a four-point contact ball bearing 23 having a positive radial clearance is used as the rolling bearing 5.

The preload is applied to the bearing 23 by appropriately using the preload applying means shown in the first to third embodiments. That is, the inner and outer rings 2 of the bearing 23
By pressing the 3a, 23b into the housing 2 or the shaft member 4, the radial clearance of the assembled bearing 23 is made negative, or the magnetic force of the magnet is used as in the first and second embodiments. Apply preload without contact.

By applying a preload using a magnet or the like, it is possible to prevent the motor from being thickened even when the preload is applied to the bearing. In order to make the four-point contact ball bearing 23,
For example, this can be achieved by adopting a gothic arc groove or the like as the shape of the raceway groove. Due to its structure, the four-point contact ball bearing 23 has a smaller axial clearance as compared with a deep groove ball bearing, so that even with the same preload, a larger load ratio ε can be exerted than a deep groove ball bearing. That is, when the load ratio ε of the bearing is maintained at 40% or more, the preload applied to the bearing can be reduced.

Further, in the case of the four-point contact type, a higher load factor can be applied even with the same magnitude of preload as compared with the two-point contact type. Other configurations, operations, and effects are the same as those described above. When the four-point contact ball bearing 23 is a bearing having a negative internal clearance in advance, a preload has already been generated inside the bearing, and the four-point contact ball bearing 23 has a sufficient load factor ε to suppress the rotational vibration of the motor. Can be made. In this case, since the preload is set in advance for the bearing itself, there is no need to apply a preload using a magnetic force. Alternatively, a configuration may be adopted in which a preload sufficient to achieve the target load factor ε is separately applied.

Next, a fifth embodiment will be described with reference to the drawings. Note that the same reference numerals are given to the same components and the like as in the above embodiment, and the description thereof will be omitted. In this embodiment, as shown in FIG. 6, a double-row angular contact ball bearing 24 is used as the rolling bearing 5. The double-row angular contact ball bearing 24 generally has a preload inside when assembled, and since it is a double-row bearing, it can have an action point distance with the same contact angle as when two bearings are used. As a result, the load factor ε becomes 40% or more, and in the present embodiment, the load factor ε is 1
An MPU cooling fan motor that supports a rotating member with a single bearing can be provided.

Even if the preload is applied to the bearing, the motor is prevented from being thickened because no preload components are required. When the load factor ε is less than 40%, a preload may be externally applied using each of the preload applying units. Further, when a double-row angular contact ball bearing 24 is used as a bearing, a 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.

In all of the above embodiments, the preload applying means may be used in combination as appropriate.

[0033]

[Example 1] With respect to the motor having the structure shown in the first embodiment and the third embodiment, when a moment load is applied to the bearing 5 by the gyro action of the fan, the load is given by the preload applied. A test was conducted for the magnitude of the rate ε and for the occurrence of abnormal noise.

Here, the test conditions are as follows: bearing: equivalent to 693, motor rotation speed: 5000 rpm, rotation rotation speed: 10 rpm.

The rotation speed is generated by inclining the motor and setting the gyro moment acting on the bearing 5 to 0.082 kgfmm. When the load factor and the presence or absence of abnormal noise in the test under the above conditions were confirmed, the results shown in Table 1 were obtained.

[0036]

[Table 1]

From Table 1, it can be seen that abnormal noise does not occur when the load factor is 40% or more, and that the noise level can be equal to or more than that of a small motor for information equipment using two bearings. That is, it can be seen that generation of abnormal noise is prevented by setting the load factor ε to 40% or more. Here, the number of balls to be incorporated in the bearing 5 is specified as five, and in the first embodiment, an axial load of 30 gf is applied to the bearing by the weight of the fan and the magnetic attraction force. In the test, the bearing was subjected to an axial load of 20 gf by the weight of the fan and the magnetic attraction force, and a test was performed under the same conditions as described above.
It was 0%, and it was naturally confirmed that no abnormal noise was generated.

[Second Embodiment] Under the same test conditions as those of the first embodiment, a test was conducted on the load factor and the occurrence of abnormal noise by changing the number of rolling elements incorporated in the bearing 5. The configuration of the bearing 5 used in the first embodiment was used. However, bearing 5
The axial load applied to was set as low as 20 gf.

Table 2 shows the results of the test.

[0040]

[Table 2]

As can be seen from Table 2, even under the same axial load condition, by specifying the number of rolling elements to five, the load ratio becomes 40% or more, and an information device using two bearings It can be understood that the noise level can be equal to or higher than that of a small-sized motor.

[0042]

As described above, when the small motor for information equipment of the present invention is used, the rotating member is supported by one bearing to which a predetermined preload is applied, so that the motor can be further thinned. And the generation of abnormal noise can be suppressed. In addition, since only one bearing is used, the torque becomes low and the rise time (the time required for the rotational speed to reach the target value)
In addition, it is possible to reduce the power consumption and the power consumption, and it is possible to achieve a noise level and durability equal to or higher than that of a small motor for information equipment that supports a rotating member with two bearings.

[Brief description of the drawings]

FIG. 1 is a view for explaining a small motor for information equipment according to a first embodiment of the present invention.

FIG. 2 is a view for explaining a small motor for information equipment according to a second embodiment of the present invention.

FIG. 3 is a diagram for explaining a small motor for information equipment according to a third embodiment of the present invention.

FIG. 4 is a view for explaining a small motor for information equipment according to a third embodiment of the present invention.

FIG. 5 is an enlarged view for explaining a small motor for information equipment according to a fourth embodiment of the present invention.

FIG. 6 is an enlarged view for explaining a small motor for information equipment according to a fifth embodiment based on the present invention.

FIG. 7 is an enlarged view for explaining a conventional small motor for information equipment.

[Explanation of symbols]

 ε Load factor 1 Frame 2 Housing 3 Stator 4 Shaft member 5 Bearing 6 Rotor case 7 Rotor magnet 8 Blade member 9 Snap ring 10 Preload spring 20 Cylindrical magnet 21 Plate member 22 Depression (slack) 23 Four-point contact bearing 24 Double row Angular contact ball bearings

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Liu Army 1-5-50 Kugenuma Shinmei, Fujisawa City, Kanagawa Prefecture Inside NSK Corporation (72) Inventor Hiroyuki Nakamura 1-5-50 Kugenuma Shinmei, Fujisawa City, Kanagawa Prefecture F term in NSK Ltd. (reference) 3J012 AB04 BB03 CB10 FB07 FB10 5H605 AA00 AA05 BB05 BB19 CC01 CC03 CC04 CC05 EA02 EA12 EB10 EB39 FF06

Claims (1)

[Claims] 1. A small motor for information equipment, wherein a rotating member of a motor is supported by one rolling bearing, and a preload is applied to the bearing.