JPH0522918A - Media driving brushless motor - Google Patents

Abstract

PURPOSE:To obtain a brushless motor for enabling surface deflection to be dimished by making the outer diameter of the base section of the bearing section of a first ball bearing, larger than the inner diameter of the intermediate section in the thickness direction, of a stator, and by moving the outer peripheral section of the base section into a relief section. CONSTITUTION:A brushless motor has a fixed base 21, a stator core 25, a bearing supporting section 27, and first and second ball bearings 43, 44. The inner peripheral section of a stator 24 is provided with first and second relief sections 34, 35 with the boundary of an inner side projected-section 31a, and into the first relief section 34, the outer peripheral section of the base section 27a of the bearing supporting section 27 is moved. Accordingly, the base section 27a of the thickness A of necessary strength, and the stator 24 can be set to be overlapped with each other, and the diameter of a first fitting channel 36 inside the base section 27a can be made large, and so the first ball bearing 43 of a large diameter can be used. Besides, inside a stator bearing section 22, the tip section 27a of the ball bearing supporting section 27 of a necessary thickness B can be set, and the second ball bearing 44 of a large diameter can be used, and so rigidity can be much improved, and so the surface deflection of a rotor 12 and a hard disc 11 can be made less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radial gap type brushless motor for driving a medium used in a device for rotating a disc type medium such as a magnetic disc or an optical disc, such as a hard disc drive.

[0002]

2. Description of the Related Art FIG. 8 shows a DC brushless motor for driving a medium which is conventionally used as a hard disk drive.

In the figure, reference numeral 1 is a fixed base made of a non-magnetic metal material, and a stator support portion 2 is integrally provided on its peripheral portion.
The fixed base 1 is press-fitted and attached to a fixed hole 3a of a lower frame 3 of a hard disk drive. The stator support portion 2 includes a ring-shaped first portion 2a that engages with an inner peripheral surface of a stator core, which will be described later, and a step-shaped second portion 2 that is continuous with a lower end of the portion 2a and engages with an end surface of the stator core.
and b.

A stator 4 is attached to the stator support portion 2 as described later. The stator 4 is formed by winding an exciting winding on each salient pole radially protruding toward the outer side in the radial direction of the stator core 5 formed by laminating a large number of core plates 5a made of a magnetic metal plate and having the same structure shown in FIG. It is formed by winding the wire 6. Therefore, the inner peripheral surface of the stator 4 has a structure in which the diameter does not change. Reference numeral 7 is slot insulation for insulating the stator core 5 and the winding wire 6 from each other.

Further, as shown in FIG. 7, some of the salient pole portions 5c projecting from the ring portion 5b are subjected to half blanking so that the respective core plates 5a are formed on one surface of the salient pole portion 5c. The convex portion is provided on the other surface and the concave portion is provided on the other surface (note that reference numeral 5d in FIG. 7 indicates a half blanking portion), and the concave portion and the convex portion are press-fitted in the core plates 5a adjacent to each other in the stacking direction. As a result, they are connected to form the stator core 5. In this stator 4, the lower end surface of the stator core 5 is brought into contact with the second portion 2b, and the lower inner peripheral surface of the core 5 is press-fitted into the outer peripheral surface of the first portion 2a. It is fixed.

A fixed shaft 8 is provided at the central portion of the fixed base 1 so as to project vertically upward through the central portion of the stator 4. The upper end of the fixed shaft 8 is connected to the upper frame 10 of the hard disk drive by a screw 9 screwed to the fixed shaft 8, so that the fixed shaft 8 is supported at both ends. The upper frame 10 and the lower frame 3 are connected to each other to form a shield case.

A rotor 12 for supporting a hard disk 11 is rotatably supported on the fixed shaft 8 via a first ball bearing 13 and a second ball bearing 14. The rotor 12 has a cup-like shape with the lower surface opened to accommodate the stator 4 therein. A rotor magnet 16 is attached to the inner peripheral surface of the peripheral cylindrical wall 15 of the rotor 12, and the rotor 12 faces downward in the center. It integrally has a protruding cylindrical bearing support portion 17. The outer diameter Z of the peripheral cylindrical wall 15 of the rotor 12 is 1
It is about 0 mm to 20 mm.

The rotor magnet 16 is a ring-shaped plastic magnet, which is magnetized along its radial direction. By this magnetization, an N pole and an S pole are circumferentially formed on the inner peripheral portion of the magnet 16. Are provided alternately along the line.
The inner peripheral surface of the rotor magnet 16 is closely opposed to the tip surfaces of the salient poles of the stator 4 via a slight air gap.

The bearing support portion 17 is disposed by being inserted between the inner peripheral surface of the stator 4 and the fixed shaft 8. This support 1
The first ball bearing 13 is provided between the base portion 17a of 7 and the tip portion of the fixed shaft 8, and the second ball bearing 13 is provided between the tip portion 17b of the bearing support portion 17 and the base portion of the fixed shaft 8. Bearing 14
Is provided. A step portion 17c is formed on the inner peripheral surface of the intermediate portion of the bearing support portion 17, and the outer races of both ball bearings 13 and 14 are axially supported by the upper and lower ends of the step portion 17c, and these ball bearings 13 and 14 are supported. It is possible to attach 14 by applying a preload. The tip end portion of the bearing support portion 17 has a slightly smaller diameter than the other portions, and is inserted and arranged inside the first portion 2a of the stator support portion 2. In addition,
In FIG. 8, reference numeral 18 is a closing ring fixedly provided on the upper end of the outer race of the first ball bearing 13.

An annular flange portion 15a is integrally provided on the outer surface of the peripheral cylindrical wall 15 and two hard disks 11, for example, are mounted above the flange portion 15a. . These disks 11
For mounting, a spacer ring 19 is provided between the two hard disks 11 fitted to the peripheral cylindrical wall 15, and a ring-shaped nut 20 is screwed onto the threaded portion formed at the upper end of the peripheral cylindrical wall 15. Combine this with the flange 15
This is done by sandwiching the two hard disks 11 and the spacer ring 19 between them and a.

In the brushless motor having the above structure, the thickness A of the base portion 17a of the bearing support portion 17 in which the first ball bearing 13 is arranged inside and the bearing support portion 17 in which the second ball bearing 14 is arranged inside are formed. The thickness B of the tip portion 17b ensures the required strength of the bearing support portion 17,
The deviation of 7 is set within the allowable value. Further, the width C (see FIG. 7) of the ring portion 5b of the stator core 5 provides a stable engagement area with the two portions 2b and secures a necessary magnetic path cross section formed between the rotor core 16 and the rotor magnet 16. In order to do so, it is formed in a predetermined size.

[0012]

In the conventional brushless motor described above, the thickness A of the base portion 17a is set in order to obtain the strength required for the base portion 17a of the bearing support portion 17 inserted and arranged inside the stator 4. It is secured inside the stator 4. Therefore, it has been unavoidable to use the first ball bearing 13 arranged inside the base portion 17a having a small outer diameter. Similarly, in order to obtain the strength required for the tip portion 17b of the bearing support portion 17, this tip portion 1
The thickness B of 7b is secured inside the first portion 2a of the stator support portion 2 positioned so as to cover the lower inner peripheral surface of the stator 4. Therefore, it is inevitable that the second ball bearing 14 arranged inside the tip portion 17b also has a small outer diameter.

By the way, the surface runout of the rotor 12 and the hard disk 11 supported by the rotor 12 is caused by the ball bearings 13 and 14.
It is known that the rigidity of the ball bearings 13 and 14 increases as the diameter of the steel balls included in the ball bearings 13 and 14 increases. Therefore, in the above-described conventional configuration in which the ball bearings 13 and 14 having a small diameter have to be used, since the rigidity is small, the hard disk 11
The surface wobbling is large, which becomes an obstacle in increasing the recording density of the disk 11.

It should be noted that, as one of measures for making it possible to use large diameter ball bearings 13 and 14 under the condition that the diameter of the rotor 12 is limited, there is a method of increasing the entire inner diameter of the stator 4. Conceivable. However, in that case, the width C of the ring portion 5b of the core plate 5a becomes thin, and therefore the ring portion 5b easily becomes magnetically saturated, and the torque is greatly reduced, which is not a preferable measure.

It is an object of the present invention to use a large diameter ball bearing for rotatably supporting a rotor without causing a significant decrease in torque, and to reduce the surface runout by a brushless motor for media drive. Is to get.

[0016]

According to the present invention, a fixed base having a stator supporting portion, a stator attached to the stator supporting portion, and a protrusion provided on the fixed base and penetrating a central portion of the stator. A cup-shaped bearing for accommodating the fixed shaft and the stator, a rotor magnet is attached to the inner peripheral surface of the peripheral cylindrical wall of the cup, and a cylindrical bearing is disposed in the center between the fixed shaft and the stator. A rotor having a support portion and having a disk-shaped medium mounted on the outer periphery of the peripheral cylindrical wall, and a first ball bearing provided between the base portion of the bearing support portion and the tip portion of the fixed shaft. When,
Radial gap type which is provided between the tip end portion of the bearing support portion and the base portion of the fixed shaft, and includes a second ball bearing that rotatably supports the rotor on the fixed shaft together with the first ball bearing. Of the brushless motor for driving the media.

In order to achieve the above object, the inner diameter of the end portion of the stator on the side of the first ball bearing is made larger than the inner diameter of the intermediate portion in the thickness direction of the stator so that the first ball bearing of the stator is formed. A relief portion is formed on the inner surface of the side end portion, and the outer diameter of the base portion of the bearing support portion in which the first ball bearing is arranged inside is made larger than the inner diameter of the intermediate portion in the thickness direction of the stator. The outer peripheral portion of is inserted into the relief portion. In the present invention, the inner diameter of the second ball bearing side end portion, which is located opposite to the clearance portion with respect to the thickness direction intermediate portion of the stator, is equal to or larger than the inner diameter of the thickness direction intermediate portion of the stator. Is the diameter.

In order to achieve the same object, the inner diameter of the end portion of the stator on the side of the second ball bearing is made larger than the inner diameter of the intermediate portion in the thickness direction of the stator, so that the second portion of the stator is formed. Form a relief on the inner surface of the ball bearing end,
The stator support portion is engaged with the relief portion so that the inner peripheral surface of the support portion and the inner peripheral surface of the intermediate portion in the thickness direction of the stator are substantially flush with each other, and the inner portion of the stator support portion is provided inside the stator support portion. You may arrange | position the front-end | tip part of a bearing support part. In the present invention, the inner diameter of the first ball bearing side end portion, which is located opposite to the escape portion with the middle portion in the thickness direction of the stator as a boundary, is equal to or larger than the inner diameter of the middle portion in the thickness direction of the stator. Is the diameter.

In order to achieve the same object, the inner diameter of the first ball bearing side end portion of the stator is made larger than the inner diameter of the thickness direction middle portion of the stator so that the first ball of the stator is formed. A first relief portion is formed on the inner surface of the bearing side end portion, and the outer diameter of the base portion of the bearing support portion in which the first ball bearing is arranged inside is made larger than the inner diameter of the intermediate portion in the thickness direction of the stator. , The outer peripheral portion of the base is the first
The inner diameter of the end of the stator on the second ball bearing side is made larger than the inner diameter of the intermediate portion in the thickness direction of the stator so that the end of the stator on the second ball bearing side of the stator is inserted. A second relief portion is formed on the inner surface, and the stator support portion is engaged with the second relief portion so that the inner peripheral surface of the support portion and the inner peripheral surface of the intermediate portion in the thickness direction of the stator are substantially flush with each other. And the tip end portion of the bearing support portion may be disposed inside the stator support portion. Further, in order to secure a necessary and sufficient magnetic path, the stator support portion may be made of a magnetic material.

[0020]

According to the present invention, the outer peripheral portion of the base portion of the bearing support portion is inserted into the relief portion formed at the end portion of the stator on the side of the first ball bearing, so that the base portion and the stator having a necessary thickness are formed. The inner peripheral portion of the first ball bearing can be provided so as to be overlapped with the inner peripheral portion of the base instead of being arranged in the radial direction, and the first ball bearing arranged inside the base portion can be enlarged according to the entry. Moreover, since the inner diameter of the portion that secures the magnetic path in the inner peripheral portion of the stator is smaller than the inner diameter of the relief portion, its width is large and the required magnetic path cross section can be secured.

According to the present invention, the stator support portion is inserted into the clearance portion formed at the end portion of the stator on the side of the second ball bearing, so that the support portion and the inner peripheral portion of the stator are aligned in the radial direction. It is possible to arrange the tip end portion of the bearing support portion having the necessary thickness inside the stator support portion by providing the tip end portion of the second ball bearing that is arranged inside the tip end portion so as not to be overlapped. Can be increased in accordance with the penetration. Moreover, since the inner diameter of the portion that secures the magnetic path in the inner peripheral portion of the stator is smaller than the inner diameter of the relief portion, its width is large and the required magnetic path cross section can be secured.

According to the third aspect of the present invention, by virtue of the effects of the first and second aspects, both the first ball bearing and the second ball bearing having a large diameter can be used, and the first and second reliefs can be used. By the axial middle part of the stator whose inner diameter is smaller than the
The required magnetic path cross section can be secured.

In the present invention, since the stator support portion engaged with the clearance formed at the end of the stator on the side of the second ball bearing is made of a magnetic material, this support portion serves as a part of the magnetic path. Can be used.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described with reference to FIGS. In the description, the same components as those of the conventional DC brushless motor described with reference to FIGS. 7 and 8 are denoted by the same reference numerals as those of the conventional example, and the description thereof will be omitted. Only the part will be described below.

The difference from the conventional example is that the fixed base 21, the stator core 25 of the stator 24, the cylindrical bearing support portion 27 of the rotor 12, and the first and second ball bearings 43, 4 are provided.
It is 4.

Fixed base 21 having the same diameter as the conventional fixed base
Is formed of a magnetic metal material, and the stator support portion 22 provided on the peripheral portion thereof has a ring-shaped first portion 22a and a second portion 22b as in the conventional example. The first part 22
The a is formed to have a thickness approximately the same as that of the second relief portion described later. The thickness of the first portion 22a can be made thicker than that of the conventional example, and the second portion 22b is narrowed accordingly.

The stator core 25 of the stator 24 has two core plates 25X and 25Y made of silicon steel plates having different inner diameters.
Are formed by stacking. The first core plate 25X is shown in FIG.
As shown in FIG. 5, a plurality of salient pole portions 5c are radially provided on the outer periphery of the ring portion 25e toward the outer side in the radial direction. The second core plate 25Y has a ring portion 25f as shown in FIG.
A plurality of salient pole portions 5c are radially provided on the outer periphery of the radially outwardly projecting portion. The ring portions 25e and 25f have the same outer diameter, but the ring portion 25f has a larger inner diameter. The first core plate 25X is the same as the core plate of the conventional example. Then, as shown in FIG. 2, a plurality of second core plates 25Y are laminated to form an intermediate core portion 31 located at an axially intermediate portion of the stator core 25. A plurality of first core plates 25X are laminated to form a first end core portion 32 laminated on one surface of the intermediate core portion 31, and a second end core portion 33 laminated on the other surface of the intermediate core portion 31. Is doing.

Therefore, the first and second end core portions 32,
The inner diameter D of 33 is formed larger than the inner diameter E of the intermediate core portion 31, so that the first relief portion 34 is provided at one end portion of the stator 24 located on the first ball bearing 23 side, The stator 2 located on the second ball bearing 24 side
A second relief portion 35 is provided at the other end portion of 4.

The stator 24 having such a configuration is attached to the fixed base 1 by engaging the second relief portion 35 with the first portion 22a of the stator support portion 22. By this attachment, the inner peripheral surface of the stator support portion 22 is
The first inner protruding portion 31a is substantially flush with the inner peripheral surface. The stator 24 is attached by press fitting,
The tip of the first portion 22 a is the inward protruding portion 3 of the intermediate core portion 31.
The first portion 22a is in contact with the lower surface of 1a and
The inner peripheral surface of the second end core portion 33 is pressed against the outer peripheral surface of, and the lower surface of the second end core portion 33 is pressed against the second portion 22b.

The bearing support portion 27 has a base portion 27a larger than the inner diameter E of the inward protruding portion 31a, and
The tip side portion having a diameter smaller than this is formed as a straight structure in which the diameter does not change. The outer peripheral portion of the base portion 27a has entered the first relief portion 34, and the base portion 2a
The thickness A between the first mounting groove 36 provided inside 7a and the outer peripheral surface of the base portion 27a has a thickness necessary for design. The first ball bearing 43 fitted into the first mounting groove 36 and mounted between the base portion 27a and the tip portion of the fixed shaft 8 has a larger outer diameter in accordance with the first relief portion 34. It is used.

The tip portion 27b of the bearing support portion 27 is inserted inside the stator support portion 22. This tip 2
Second mounting groove 37 and tip portion 27b provided inside 7b
The thickness B between the outer peripheral surface and the outer peripheral surface has a thickness necessary for design. The second ball bearing 44 fitted into the second mounting groove 37 and mounted between the tip portion 27b and the base portion of the fixed shaft 8 has a larger outer diameter in accordance with the second relief portion 35. It is used.

According to the DC brushless motor having the structure described above, the inward protruding portion 3 is provided on the inner peripheral portion of the stator 24.
The first and second relief portions 34 and 35 are provided at the boundary 1a, and the base portion 27a of the bearing support portion 27 is provided in the first relief portion 34.
The outer periphery of the Therefore, the base 27a and the stator 2 having the thickness A for obtaining the required strength are provided.
4 and 4 can be provided so as not to be aligned in the radial direction but to overlap. Therefore, the diameter of the first mounting groove 36 provided inside the base portion 27 can be increased according to the entry of the base portion 27a into the first relief portion 34, and accordingly, the large diameter first ball including the steel ball with a large diameter is provided. Bearings 43 can be used.

At the same time, by inserting the stator support portion 22 into the second relief portion 35 of the stator 24,
The support portion 22 and the stator 24 are provided so as not to be aligned in the radial direction but to overlap each other, and the tip end portion 27a of the bearing support portion 27 having a required thickness B is provided inside the stator support portion 22. it can. Therefore, this tip 27
Since b can be made thick, the second mounting groove 37 provided inside can be made large in diameter in accordance with the intrusion, and accordingly, a large diameter second ball bearing 44 including a steel ball having a large diameter can be used.

As described above, since the first and second bearings 43 and 44 having large diameters can be adopted, the rigidity thereof can be greatly improved and the surface runout of the rotor 12 and the hard disk 11 can be reduced. Since this surface runout preventing action can be realized even when one of the first and second ball bearings 43, 44 has a large diameter, the purpose is particularly achieved in the configuration in which both of them have a large diameter. The degree is high.

Then, the first and second escape portions 34, 3
With the provision of 5, the first and second end core portions 31,
Although the width f (see FIG. 5) and the cross-sectional area of the ring portion 25 f at 32 are small, the stator 24 has the inward protruding portion 31 a formed by the ring portion 25 e having the wide width C of the intermediate core portion 31. Since it has, the magnetic flux can be mainly passed through this portion. Therefore, the necessary and sufficient magnetic path cross-sectional area can be secured and magnetic saturation will not occur,
There is no significant reduction in torque.

Moreover, since the stator support portion 22 made of a magnetic material is engaged with the second escape portion 35, the magnetic flux can pass through the ring portion 25f and the first portion 22a as shown by the arrow in FIG. Therefore, it is possible to compensate for the narrowing of the ring portion 25f by the first portion 22a, which is particularly advantageous in eliminating a substantial decrease in torque.

Further, since the second relief portion 35 can be provided with a thickness within the width of the ring portion 25f, the thickness B of the first portion 22a of the stator support portion 22 that engages with the second relief portion 35 can be increased (for comparison, see FIG. In the conventional case shown in FIG. 8, the first portion 2 a that overlaps with the inner peripheral surface of the lower end portion of the stator 4 is the tip portion 17 a of the bearing support portion 17.
It was constrained by the required thickness, and had to be made quite thin. ). Therefore, the strength of the stator support portion 22 is increased, and the stator 24 can be supported straight and stably.

As shown in FIG. 1, in the structure in which the tip end portion 27a of the bearing support portion 27 is inserted and arranged inside the stator support portion 22, as long as the support strength of the fixed shaft 8 with respect to the fixed base 21 is not impaired. The insertion depth can be increased. In other words, it is possible to lengthen the distance between the pair of upper and lower ball bearings 43, 44, which can further reduce the surface runout of the rotor 12 and the hard disk 11.

[0039]

Since the present invention is constructed as described above, it has the following effects.

In the brushless motor for driving media according to the first aspect of the present invention, since the first ball bearing provided between the tip of the fixed shaft and the base of the bearing support of the rotor can have a large diameter, the rotor or the like can be used. The surface runout can be reduced, and the required magnetic path cross section at the inner peripheral portion of the stator can be secured, so that the torque is not significantly reduced.

In the brushless motor for driving the medium according to the second aspect, since the second ball bearing provided between the base of the fixed shaft and the tip of the bearing support of the rotor can have a large diameter, the rotor or the like can be used. The surface runout can be reduced, and the required magnetic path cross section at the inner peripheral portion of the stator can be secured, so that the torque is not significantly reduced.

In the brushless motor for driving media according to a third aspect of the present invention, the first ball bearing provided between the tip of the fixed shaft and the base of the bearing support of the rotor, and the base of the fixed shaft and the bearing support of the rotor. A large diameter ball bearing can be used for each of the second ball bearings provided between the rotor and the tip of the rotor so that the surface runout of the rotor etc. can be reduced and the necessary magnetic path cross section at the inner peripheral portion of the stator can be secured. By doing so, the torque is not significantly reduced.

In the brushless motor for driving media according to the fourth aspect of the present invention, since the stator supporting portion can be used as the magnetic path in the inner peripheral portion of the stator, the necessary and sufficient magnetic path can be secured and the decrease in torque can be extremely reduced. .

[Brief description of drawings]

FIG. 1 is a vertical sectional side view of an entire brushless motor according to an embodiment of the present invention.

FIG. 2 is a vertical sectional side view of a stator core included in the brushless motor according to the embodiment.

FIG. 3 is a plan view of a stator core of the same embodiment.

FIG. 4 is a plan view of a first core plate included in the stator core according to the embodiment.

FIG. 5 is a plan view of a second core plate included in the stator core according to the embodiment.

FIG. 6 is a cross-sectional view for explaining a magnetic path on the stator core side of the brushless motor of the embodiment.

FIG. 7 is a plan view of a core plate included in a stator according to a conventional example.

FIG. 8 is a vertical cross-sectional side view of the entire brushless motor according to a conventional example.

[Explanation of symbols]

8 ... Fixed axis, 11 ... Hard disk (media), 12
... rotor, 15 ... peripheral cylindrical wall, 16 ... rotor magnet, 21 ... fixed base, 22 ... stator support, 24 ...
Stator, 27 ... Bearing support part, 27a ... Base part, 27b ...
Tip portion, 34 ... First relief portion, 35 ... Second relief portion, 43 ...
First ball bearing, 44 ... Second ball bearing.

Claims (4)

[Claims] 1. A fixed base having a stator support,
A stator attached to the stator support portion, a fixed shaft protruding from the fixed base and penetrating the central portion of the stator, and a cup shape for accommodating the stator, and an inner peripheral surface of a peripheral cylindrical wall thereof. A rotor magnet is attached to the shaft, and a cylindrical bearing support portion disposed between the fixed shaft and the stator is provided in the central portion, and a disk-shaped medium is attached to the outer periphery of the peripheral cylindrical wall. A rotor, a first ball bearing provided between the base of the bearing support and the tip of the fixed shaft, and a first ball bearing provided between the tip of the bearing support and the base of the fixed shaft, A radial gap type media drive brushless motor comprising: a first ball bearing, and a second ball bearing that rotatably supports the rotor on the fixed shaft, wherein an end of the stator on the side of the first ball bearing is provided. The inner diameter of the stator is larger than the inner diameter of the intermediate portion in the thickness direction of the stator to form a clearance portion on the inner surface of the end portion of the stator on the side of the first ball bearing, and the first ball bearing is arranged inside. A brushless motor for driving a medium, wherein an outer diameter of a base portion of the bearing support portion is made larger than an inner diameter of an intermediate portion in the thickness direction of the stator, and an outer peripheral portion of the base portion is inserted into the escape portion. 2. A fixed base having a stator support portion,
A stator attached to the stator support portion, a fixed shaft protruding from the fixed base and penetrating the central portion of the stator, and a cup shape for accommodating the stator, and an inner peripheral surface of a peripheral cylindrical wall thereof. A rotor magnet is attached to the shaft, and a cylindrical bearing support portion disposed between the fixed shaft and the stator is provided in the central portion, and a disk-shaped medium is attached to the outer periphery of the peripheral cylindrical wall. A rotor, a first ball bearing provided between the base of the bearing support and the tip of the fixed shaft, and a first ball bearing provided between the tip of the bearing support and the base of the fixed shaft, A radial gap type media drive brushless motor comprising a first ball bearing and a second ball bearing that rotatably supports the rotor on the fixed shaft, wherein an end of the stator on the side of the second ball bearing is provided. The inner diameter of the stator is larger than the inner diameter of the intermediate portion in the thickness direction of the stator to form an escape portion on the inner surface of the end of the stator on the side of the second ball bearing, and the escape portion is engaged with the stator support portion. The inner peripheral surface of the support portion and the inner peripheral surface of the intermediate portion in the thickness direction of the stator are substantially flush with each other, and the tip end portion of the bearing support portion is disposed inside the stator support portion. A brushless motor for media drive characterized by. 3. A fixed base having a stator support portion,
A stator attached to the stator support portion, a fixed shaft protruding from the fixed base and penetrating the central portion of the stator, and a cup shape for accommodating the stator, and an inner peripheral surface of a peripheral cylindrical wall thereof. A rotor magnet is attached to the shaft, and a cylindrical bearing support portion disposed between the fixed shaft and the stator is provided in the central portion, and a disk-shaped medium is attached to the outer periphery of the peripheral cylindrical wall. A rotor, a first ball bearing provided between the base of the bearing support and the tip of the fixed shaft, and a first ball bearing provided between the tip of the bearing support and the base of the fixed shaft, A radial gap type media drive brushless motor comprising: a first ball bearing, and a second ball bearing that rotatably supports the rotor on the fixed shaft, wherein an end of the stator on the side of the first ball bearing is provided. The inner diameter of the stator is larger than the inner diameter of the intermediate portion in the thickness direction of the stator to form a first clearance portion on the inner surface of the end portion of the stator on the side of the first ball bearing, and the first ball bearing is arranged inside. The outer diameter of the base portion of the bearing support portion is larger than the inner diameter of the intermediate portion in the thickness direction of the stator, and the outer peripheral portion of the base portion is allowed to enter the first relief portion, and the second portion of the stator is provided.
The inner diameter of the end portion on the ball bearing side is made larger than the inner diameter of the middle portion in the thickness direction of the stator to form a second relief portion on the inner surface of the end portion on the second ball bearing side of the stator. Is engaged with the stator support portion so that the inner peripheral surface of the support portion and the inner peripheral surface of the intermediate portion in the thickness direction of the stator are substantially flush with each other, and the bearing support is provided inside the stator support portion. A brushless motor for driving a medium, characterized in that a tip portion of the portion is arranged. 4. The brushless motor for driving a medium according to claim 2, wherein the stator support portion is made of a magnetic material.