JP2003111324A - Rotor of direct-current brushless motor, blower, and air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To structurally ensure fixing strength for magnets in the direction of revolution and in the axial direction, and further to enhance the concentricity between the magnets and a back yoke. SOLUTION: Whirl-stop recesses which extend from the one-side end of the back yoke in the axial direction to a midpoint in the axial direction are formed in the circumferential surface of the back yoke in the axial direction. Whirl-stop projections are formed on the inner circumferential surface of the ring-shaped magnet of a rotor in the axial direction. The whirl-stop projections are fit into the whirl-stop recesses to cause the projections and the recesses to function as a whirl-stop in the direction of revolution and further as a coming-off stopper for preventing the ring-shaped magnet of the rotor from coming-off to the other-side end in the axial direction. Further, coming-off preventing members which function to prevent the ring-shaped magnet of the rotor from coming-off to the one-side end in the axial direction. In addition, clearance adjusting projections for adjusting and uniformizing the clearance between the magnet and the back yoke are formed on the inner circumferential surface of the ring-shaped magnet of the rotor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotor of a DC brushless motor used as a drive source for a blower fan of an air conditioner or the like.

[0002]

2. Description of the Related Art In recent years, for example, a DC brushless motor whose rotation speed is easily controlled and which has high efficiency has been widely used as a driving motor for a blower fan of an air conditioner.

FIG. 5 is a Japanese Patent Application No. 2001-2 filed by the applicant.
It is sectional drawing which shows the DC brushless motor which used the conventional permanent magnet described in 37801. This DC brushless motor is of a type in which a magnet is arranged on the surface of a rotor. In the figure, 1 is a rotor, 2 is a back yoke having an axial hole in the center, and 3 is a rotor-shaped magnet of the rotor provided on the outer peripheral surface of the back yoke 2, and uses a plastic magnet. Reference numeral 4 is a position detecting magnet, 5 is a shaft fitted into the shaft hole of the back yoke 2 by press fitting, etc., 6 is provided on both sides of the rotor 1, and the shaft 5
The bearing is press-fitted into the bearing, 7 is a retaining ring for the bearing, 8 is a magnet fixing part fitted to the shaft 5 and fitted to the position detecting magnet 4, and the position detecting magnet 4 is attached to the axial end portion of the back yoke 2. Abut and fix. One bearing 6 is brought into contact with the end of the magnet fixing component 8 opposite to the position detecting magnet 4 side.

A spacer 9 is provided between the axial end of the back yoke 2 and the position detecting magnet 4.
Reference numeral 10 is a Hall IC as an example of a magnetic detection element provided at a position facing the position detection magnet 4 on the side of the stator 11.
(Integrated Circuit), 12 is a mold resin, and 13 is a DC brushless motor.

In the DC brushless motor configured as described above, the distance between the position detecting magnet 4 and the Hall IC is determined by the length of the magnet fixing component 8.
The distance between the position detecting magnet 4 and the Hall IC can be accurately assembled. As a result, the position detection failure of the rotor 1 can be reduced and the position of the rotor 1 can be accurately detected, so that the controllability and performance of the DC brushless motor can be improved.

The ring-shaped magnet 3 of the rotor is fixed to the back yoke 2 by adhesion, and the fixing strength in the rotation direction and the axial direction is obtained only by adhesion. Since the ring-shaped magnet 3 of the rotor is a resin molded product, the dimensional variation is larger than that of the back yoke 2, and it is necessary to make a large gap with the outer diameter of the back yoke 2.

[0007]

Since the conventional DC brushless motor using a permanent magnet is constructed as described above, it has the following problems. (1) Due to variations in adhesion, the fixing strength between the ring-shaped magnet 3 of the rotor and the back yoke 2 has low reliability in both the rotation direction and the axial direction. (2) Since it is necessary to make a large gap between the ring-shaped magnet 3 of the rotor and the back yoke 2, it is difficult to obtain coaxiality between the ring-shaped magnet 3 of the rotor and the back yoke 2, and the air gap is uneven. In addition, imbalance also occurs, which causes deterioration of characteristics and noise and vibration.

The present invention has been made in order to solve the above-mentioned problems, and structurally secures the fixing strength in the rotation direction and the axial direction of the ring-shaped magnet of the rotor, and the reliability, DC brushless motor rotor with improved quality and improved quality by uniformly adjusting the clearance between the ring-shaped magnet of the rotor and the back yoke to improve coaxiality. And a fan and an air conditioner.

[0009]

A rotor of a DC brushless motor according to the present invention is a DC brushless motor rotor having a rotor ring magnet fixed to an outer peripheral surface of a back yoke by adhesion. In addition to providing an anti-rotation recess formed in the outer periphery of the yoke in the axial direction, an axial anti-rotation protrusion on the inner circumference of the rotor ring-shaped magnet, and an anti-rotation protrusion in the anti-rotation recess. It is characterized in that it is fitted with a stopper to prevent rotation in the rotation direction.

Further, the rotor of the DC brushless motor according to the present invention is a DC brushless motor rotor having a ring-shaped magnet of the rotor which is fixed to the outer peripheral surface of the back yoke by adhesion. A detent recess formed in the axial direction is formed from one axial end of the back yoke halfway in the axial direction, and a detent protrusion is formed on the inner circumference of the ring-shaped magnet of the rotor in the axial direction. Then, the protrusion of the rotation stopper is fitted in the recess of the rotation stopper to prevent rotation in the rotation direction, and to prevent the ring-shaped magnet of the rotor from coming off to the other axial end side. Is characterized by.

Further, the rotor of the DC brushless motor according to the present invention is provided with a retaining member for retaining the ring-shaped magnet of the rotor toward one axial end portion side. .

Further, the rotor of the DC brushless motor according to the present invention is a rotor of a DC brushless motor having a rotor-shaped magnet arranged on the outer peripheral surface of the back yoke. A detent recess formed in the back yoke is formed from one axial end of the back yoke to an intermediate position in the axial direction, and a detent protrusion is formed in the axial direction on the inner circumference of the ring-shaped magnet of the rotor, The protrusion of the rotation stopper is fitted in the recess of the rotation stopper to prevent rotation, and the ring-shaped magnet of the rotor is prevented from coming off to the other end in the axial direction. It is characterized in that it is provided with a retaining member for retaining the ring-shaped magnet of the rotor toward the end portion in the axial direction.

Further, in the rotor of the DC brushless motor according to the present invention, the retaining member is formed of a retaining yoke which is different from the retaining yoke to which the ring-shaped magnet of the rotor is fixed. Is characterized by.

The rotor of the DC brushless motor according to the present invention is characterized in that the retaining member is made of a plastic molded product.

In the rotor of the DC brushless motor according to the present invention, the position detecting magnet is provided at the axial end of the back yoke so as to face the magnetic detecting element on the stator side, and the retaining member is positioned. It is characterized by being composed of a detection magnet.

Further, the rotor of the DC brushless motor according to the present invention is characterized in that the position detecting magnet has a U-shaped cross section.

Further, the rotor of the DC brushless motor according to the present invention is a rotor of a DC brushless motor, which has a ring-shaped magnet of the rotor fixed to the outer peripheral surface of the back yoke by adhesion. The inner circumference of the magnet is provided with a clearance adjusting projection for uniformly adjusting the clearance with the back yoke.

Further, the rotor of the DC brushless motor according to the present invention is characterized in that three or more clearance adjusting protrusions are provided.

Further, the rotor of the DC brushless motor according to the present invention is characterized in that the clearance adjusting convex portion is sized so as to be scraped off when the back yoke is inserted.

The rotor of the DC brushless motor according to the present invention is the rotor of the DC brushless motor according to any one of claims 1 to 8, wherein the back yoke is provided on the inner circumference of the ring-shaped magnet of the rotor. It is characterized in that a protrusion for adjusting the clearance is provided to uniformly adjust the clearance between and.

The blower according to the present invention is defined by claims 1 to 12.
And a DC brushless motor using the rotor of the DC brushless motor according to any one of 1.

An air conditioner according to the present invention has a thirteenth aspect.
It is characterized by using the blower described in 1.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. Embodiment 1. 1 to 3 are views showing Embodiment 1, FIG. 1 is a sectional view of a DC brushless motor, FIG. 2 is a sectional view showing a rotor of a DC brushless motor, and FIG. 3 is a part of a rotor of a DC brushless motor. FIG. 3 is an exploded perspective view excluding the parts of FIG. In the figure, 1 is a rotor, 2 is a first back yoke composed of laminated caulks having a shaft hole at the center, and 2
Reference numeral a denotes a rotation preventing recess formed in the outer periphery of the first back yoke 2 from one axial end to a midpoint in the axial direction, and 3 is fixed to the outer peripheral surface of the first back yoke 2 by adhesion. It is a ring-shaped magnet of the rotor and uses a plastic magnet. Denoted at 3a is a protrusion for detent fitted into the recess 2a for detent. Reference numeral 3b is a clearance adjusting protrusion for uniformly adjusting the clearance with the first back yoke 2 provided on the inner circumference of the ring-shaped magnet 3 of the rotor. The shape of the protrusion 3a of the rotation stopper is a polygonal shape or a round shape. Further, the height of the protrusion of the rotation preventing protrusion 3a is at most about the thickness of the ring-shaped magnet 3 of the rotor. Thereby, the moldability of the ring-shaped magnet 3 of the rotor can be secured.

Reference numeral 14 denotes the first back yoke 2 so that the ring-shaped magnet 3 of the rotor does not come off in the axial direction after the ring-shaped magnet 3 of the rotor is fitted into the first back yoke 2. It is a second back yoke which is an example of a retaining member that comes into contact with one axial end of the anti-rotation recess 2a. The second back yoke 14 is
It is fixed to the first back yoke 2 by adhesion, fixed by laminating caulking, or fixed to the shaft 5 by caulking, press fitting, or the like. Here, the second back yoke 14 is shown as a yoke formed by laminating electromagnetic steel sheets, but a plastic molded product may be used.

Reference numeral 4 is a position detecting magnet, 4a is a rotation preventing projection, 5 is a shaft fitted in the shaft hole of the back yoke 2 by caulking, press fitting, etc., 6 is provided on both sides of the rotor 1,
The bearing is press-fitted into the shaft 5, 7 is a bearing retaining ring, 8 is a magnet fixing part fitted to the shaft 5 and fitted to the position detecting magnet 4, and the position detecting magnet 4 is connected to the second back yoke 14. It is fixed by abutting on the axial end of the. One bearing 6 is brought into contact with the end of the magnet fixing component 8 opposite to the position detecting magnet 4 side. 10 is a Hall IC which is an example of a magnetic detection element provided at a position facing the position detecting magnet 4 on the side of the stator 11, 12 is a mold resin, and 13 is a DC brushless motor.

The position detecting magnet 4 is attached to the back yoke 2
As one means for contacting and fixing the end portion of the second back yoke 14 in the axial direction, a protrusion 4a is provided on the contact surface of the position detecting magnet 4 with the second back yoke 14, and the end portion of the second back yoke 14 in the axial direction is fixed. It is fitted into the provided hole 14a.

By fitting the shaft 5 into the first back yoke 2 by caulking, press fitting, etc., and by fitting the convex portion 3a of the detent into the concave portion 2a of the detent, the ring-shaped magnet 3 of the rotor is first divided. Of the rotor, and the ring-shaped magnet 3 of the rotor is fixed to the first back yoke 2 by adhesion. By fitting the protrusion 3a of the detent and the recess 2a of the detent, the ring-shaped magnet 3 of the rotor becomes a detent in the rotation direction, and not only the adhesion but also the structural fixing strength can be secured. In addition, the anti-rotation recess 2
Since a is bored from one axial end to a midpoint in the axial direction, the ring-shaped magnet 3 of the rotor is prevented from coming off to the other axial end.

Anti-rotation protrusion 3a and anti-rotation recess 2a
Shows the one provided in a part in the axial direction, but may be provided in the entire axial length of the ring-shaped magnet 3 of the rotor. As a result, at least the ring-shaped magnet 3 of the rotor
It will prevent rotation in the direction of rotation.

When the ring-shaped magnet 3 of the rotor is inserted into the first back yoke 2, the clearance between the ring-shaped magnet 3 of the rotor and the first back yoke 2 is made uniform by the clearance adjusting protrusion 3b. It is adjusted to and the coaxiality is secured.
The clearance adjusting protrusions 3b are of a size that can be scraped off when the first back yoke 2 is inserted, and are provided in three or more locations evenly in the circumferential direction. As a result, the clearance between the first back yoke 2 and the ring-shaped magnet 3 of the rotor is adjusted uniformly, and the coaxiality is improved, so that the motor characteristics are improved, the occurrence of sound vibration is reduced, and the quality is improved. To do.

After the ring-shaped magnet 3 of the rotor is fixed to the first back yoke 2, one axial end portion of the first back yoke 2 in which the rotation preventing recess 2a is bored,
The second back yoke 14 is fixed. The second back yoke 14 is fixed to the first back yoke 2 by adhesion, fixed by stacking caulking, or fixed to the shaft 5 by caulking, press fitting, or the like. As a result, the ring-shaped magnet 3 of the rotor is prevented from coming off to the one axial end side where the rotation preventing recess 2a is formed.

Then, the projection 4 of the position detecting magnet 4
a is fitted into a hole 14a provided in the second back yoke 14, and the position detecting magnet 4 is attached to the second back yoke 1.
Fix at 4. Further, the magnet fixing component 8 is fitted to the position detecting magnet 4.

According to the above-described embodiment, by fitting the protrusion 3a of the detent and the recess 2a of the detent, the ring-shaped magnet 3 of the rotor becomes a detent in the rotating direction.
Not only adhesion but also structural strength can be secured. Also,
Since the anti-rotation recess 2a is bored from one end in the axial direction to the middle in the axial direction, the ring-shaped magnet 3 of the rotor is prevented from coming out toward the other end in the axial direction.
Further, the second back yoke 14 is fixed to one axial end portion of the first back yoke 2 where the rotation preventing recess 2a is formed, so that the rotation preventing recess 2a is formed. Rotor ring-shaped magnet 3 toward the axial end of the rotor
To prevent it from coming off.

When the rotation detent and the ring magnet 3 of the rotor on both sides in the axial direction are prevented from coming off, the ring magnet 3 of the rotor is fixed to the first back yoke 2. Adhesion is not always necessary.

According to the above-described embodiment, the clearance-adjusting convex portion 3b ensures the coaxiality between the ring-shaped magnet 3 of the rotor and the first back yoke 2, improves the motor characteristics, and improves the sound vibration. The quality is improved by reducing the occurrence of.

Embodiment 2. FIG. 4 is a view showing the second embodiment and is a cross-sectional view showing a rotor of a DC brushless motor. The difference from the first embodiment is that the back yoke 20 is not divided. Instead, the shape of the position detection magnet 4 is changed so that the position detection magnet 4 causes the axial removal of the ring-shaped magnet 3 of the rotor. Prevent. The position detecting magnet 4 serves as a retaining member.

As shown in the figure, the position detecting magnet 4
Has a U-shaped cross section, and is fixed so as to cover one end in the axial direction of the back yoke 20 where the recess 20a for rotation prevention is formed, and the end of the position detecting magnet 4 has a ring shape of the rotor. The protrusion 3a of the rotation stopper of the magnet 3 is pressed to prevent the ring-shaped magnet 3 of the rotor from coming off in the axial direction.

According to the above-described embodiment, the first embodiment
The same effect as that of the second back yoke 1 is obtained.
Since four or equivalent parts are not required, the structure is simple and the cost is low, and the assembling process can be simplified.

In the above-mentioned embodiments, the plastic magnet is used as the ring-shaped magnet 3 of the rotor, but the present invention is not limited to this. For example, a ferrite sintered magnet or a rare earth magnet is used. And so on.

In the above-described embodiment, the Hall IC 10 is used as the magnetic detection element, but other elements may be used. Further, the DC brushless motor using the position detecting magnet has been described, but the present invention is also applied to a sensorless DC brushless motor.

Further, the anti-rotation protrusion 3a may be press-fitted into the anti-rotation recess 2a so as not to be adhered to prevent the axial disengagement.

Further, the permanent magnet constituting one magnetic pole of the ring-shaped magnet 3 of the rotor has a shape in which both axial end portions are convex toward each end side, and the axial length of the permanent magnet is the pole center. The present invention may be applied to a rotor of a DC brushless motor configured such that the vicinity thereof is long and gradually becomes shorter toward the circumferential end portion. The reliability and quality of the rotor of the DC brushless motor are improved, and the vibration and noise of the DC brushless motor are reduced.

If the DC brushless motor blower using the rotor shown in the above-mentioned embodiment is mounted, the reliability and quality of the blower can be improved.

If the blower equipped with the DC brushless motor described above is used in an air conditioner, the reliability and quality of the air conditioner can be improved.

[0044]

The rotor of the DC brushless motor according to the present invention is provided with an anti-rotation recess formed in the outer circumference of the back yoke in the axial direction and in the axial direction of the inner circumference of the ring-shaped magnet of the rotor. By providing the protrusion of the rotation stopper and fitting the protrusion of the rotation stopper into the recess of the rotation stopper to prevent rotation, the fixing strength in the rotation direction of the ring magnet of the rotor is not only bonded but also the structure. Reliability, quality is improved.

Further, in the rotor of the DC brushless motor according to the present invention, the rotation preventing recess formed in the outer periphery of the back yoke in the axial direction is formed from one axial end of the back yoke to the middle of the axial direction. The ring-shaped magnet of the rotor is formed with an anti-rotation protrusion in the inner circumference of the magnet, and the anti-rotation protrusion is inserted into the anti-rotation recess to prevent the rotation in the other direction. Since the ring-shaped magnet of the rotor is prevented from coming off from the end side, the rotational strength of the ring-shaped magnet of the rotor and the fixing strength in the axial direction of one side are not only bonded but also structurally Since it can be secured, reliability and quality are improved.

Further, the rotor of the DC brushless motor according to the present invention is provided with the retaining member for retaining the ring-shaped magnet of the rotor toward the one end in the axial direction. The fixing strength in the rotation direction and the axial direction of the ring-shaped magnet can be structurally secured as well as bonded, so that the reliability and quality are improved.

Further, in the rotor of the DC brushless motor according to the present invention, the ring-shaped magnet of the rotor is arranged on the outer peripheral surface of the back yoke, and the rotation preventing recess is axially bored on the outer periphery of the back yoke. Is formed from one axial end of the back yoke to a midpoint in the axial direction, and a convex portion for preventing rotation is formed in the axial direction on the inner circumference of the ring magnet of the rotor, and a convex portion for preventing rotation is formed in the concave portion for preventing rotation. Part is fitted to prevent rotation in the rotation direction, and to prevent the ring-shaped magnet of the rotor from coming off to the other axial end side, and the rotor to one axial end side. By providing a retaining member that prevents the ring-shaped magnet from coming off, the rotation direction of the ring-shaped magnet of the rotor
Since the axial fixing strength on one side can be structurally secured without using an adhesive, reliability and quality are improved.

Further, in the rotor of the DC brushless motor according to the present invention, the retainer prevention member is constituted by a retainer prevention back yoke different from the back yoke to which the ring-shaped magnet of the rotor is fixed. As a result, the same parts as those of the back yoke can be used, which facilitates manufacturing.

Further, in the rotor of the DC brushless motor according to the present invention, since the retaining member is made of a plastic molded product, the weight of the rotor is reduced.

Further, in the rotor of the DC brushless motor according to the present invention, since the retaining member is constituted by the position detecting magnet, the number of parts can be reduced, the cost is reduced, and the assembling process is simplified. it can.

Further, in the rotor of the DC brushless motor according to the present invention, since the position detecting magnet has a U-shaped cross section, the end of the position detecting magnet presses the ring-shaped magnet of the rotor. be able to.

Further, in the rotor of the DC brushless motor according to the present invention, a clearance adjusting convex portion for uniformly adjusting the clearance with the back yoke is provided on the inner circumference of the ring-shaped magnet of the rotor. This improves the coaxiality between the back yoke and the ring-shaped magnet of the rotor,
The motor characteristics are improved, the generation of sound vibration is reduced, and the quality is improved.

Further, the rotor of the DC brushless motor according to the present invention is provided with three or more clearance adjusting protrusions, so that the coaxiality between the back yoke and the ring-shaped magnet of the rotor is improved in the entire circumferential direction. To do.

Further, in the rotor of the DC brushless motor according to the present invention, the clearance adjusting convex portion has a size such that it is scraped off when the back yoke is inserted, so that the back yoke and the ring-shaped magnet of the rotor are separated from each other. The gap can be made uniform.

The rotor of the DC brushless motor according to the present invention is the rotor of the DC brushless motor according to any one of claims 1 to 8, wherein the back yoke is provided on the inner circumference of the ring-shaped magnet of the rotor. By providing the clearance adjusting convex portion for uniformly adjusting the clearance between and, the motor characteristics are improved, the occurrence of sound vibration is reduced, and the quality is improved in addition to the effects of each claim.

The blower according to the present invention is defined by claims 1 to 12.
By installing the DC brushless motor using the rotor of the DC brushless motor described in any one of the above, it is possible to improve the reliability and quality of the blower.

An air conditioner according to the present invention has a thirteenth aspect.
By using the blower described in (1), the reliability and quality of the air conditioner can be improved.

[Brief description of drawings]

FIG. 1 shows the first embodiment and is a cross-sectional view of a DC brushless motor.

FIG. 2 is a view showing the first embodiment and is a cross-sectional view showing a rotor of a DC brushless motor.

FIG. 3 is a diagram showing the first embodiment and is an exploded perspective view of the rotor of the DC brushless motor with some parts removed.

FIG. 4 is a view showing the second embodiment and is a cross-sectional view showing a rotor of a DC brushless motor.

FIG. 5 is a sectional view showing a DC brushless motor using a conventional permanent magnet.

[Explanation of symbols]

1 rotor, 2nd back yoke, 2a concave part for detent, 3 ring-shaped magnet for rotor, 3a convex part for detent, 3b convex part for clearance adjustment, 4 position detecting magnet, 4a detent Protrusions, 5 shafts, 6 bearings, 7 bearing retaining rings, 8 magnet fixing parts, 10
Hall IC, 11 stator, 12 mold resin, 1
3 DC brushless motor, 14 2nd back yoke, 14a rotation stop hole, 20 back yoke, 20a
Anti-rotation recess.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Mineo Yamamoto             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. (72) Inventor Togo Yamazaki             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. (72) Inventor Takashi Matsunaga             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. (72) Inventor Hitoshi Kawaguchi             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. (72) Inventor Atsushi Matsuoka             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. F term (reference) 5H019 AA04 AA06 BB01 BB05 BB15                       BB19 BB22 BB30 CC03 CC10                       EE01                 5H622 CA01 CA05 CA10 DD04 PP03                       PP10 PP19 QA10

Claims (14)

[Claims] 1. A rotor for a DC brushless motor having a ring-shaped magnet of a rotor fixed to an outer peripheral surface of a back yoke by adhesion, wherein a detent recess formed axially in the outer periphery of the back yoke. With the provision of a rotation-stopping protrusion in the axial direction of the inner circumference of the ring-shaped magnet of the rotor, the rotation-stopping protrusion is fitted in the rotation-prevention recess to form a rotation-stop. Characteristic DC brushless motor rotor. 2. A rotor for a DC brushless motor having a ring-shaped magnet of a rotor fixed to an outer peripheral surface of a back yoke by adhesion, wherein a detent recess formed axially in the outer periphery of the back yoke. Is formed from one axial end of the back yoke to an intermediate position in the axial direction, a protrusion for preventing rotation is formed in the axial direction of the inner circumference of the ring-shaped magnet of the rotor, and a recess for preventing rotation is formed in the recess. A direct current brushless, characterized in that the protrusion of the rotation stopper is fitted into the rotation stopper to prevent rotation, and the ring-shaped magnet of the rotor is prevented from coming off to the other end in the axial direction. Motor rotor. 3. The DC brushless motor according to claim 2, further comprising a retaining member that prevents the ring-shaped magnet of the rotor from coming off to the one axial end portion side. Rotor. 4. A rotor of a DC brushless motor having a ring-shaped magnet of a rotor arranged on an outer peripheral surface of a back yoke, wherein a rotation-stop concave portion axially bored on the outer periphery of the back yoke is provided. It is formed from one axial end of the back yoke to a midpoint in the axial direction, and a convex portion for preventing rotation is formed in the axial direction on the inner circumference of the ring-shaped magnet of the rotor, and the rotation stopper is provided in the concave portion for preventing rotation. Of the ring-shaped magnet of the rotor to the other end in the axial direction while preventing the ring-shaped magnet of the rotor from slipping off to the other end in the axial direction. A rotor for a DC brushless motor, comprising: a retaining member for preventing a ring-shaped magnet of the rotor from coming off. 5. The retainer prevention member is constituted by a retainer prevention back yoke different from the back yoke to which the ring-shaped magnet of the rotor is fixed. The rotor of the DC brushless motor according to 4. 6. The rotor for a DC brushless motor according to claim 3, wherein the retaining member is formed of a plastic molded product. 7. A position detecting magnet is provided at an axial end of the back yoke so as to face a magnetic detecting element on the stator side, and the retaining member is formed of the position detecting magnet. The rotor of the DC brushless motor according to claim 3 or 4. 8. The rotor for a DC brushless motor according to claim 7, wherein the position detecting magnet has a U-shaped cross section. 9. A rotor of a DC brushless motor having a rotor ring-shaped magnet fixed to the outer peripheral surface of the back yoke by adhesion, wherein the back yoke is provided on the inner periphery of the ring-shaped magnet of the rotor. A rotor for a DC brushless motor, which is provided with a clearance adjusting protrusion for uniformly adjusting the clearance. 10. The rotor for a DC brushless motor according to claim 9, wherein three or more protrusions for adjusting the clearance are provided. 11. The rotor for a DC brushless motor according to claim 9, wherein the clearance adjusting protrusion has a size such that it is scraped off when the back yoke is inserted. 12. A clearance adjusting convex portion for uniformly adjusting a clearance with the back yoke is provided on an inner circumference of a ring-shaped magnet of the rotor. A rotor of the DC brushless motor according to any one of claims. 13. A blower comprising a DC brushless motor using the rotor of the DC brushless motor according to claim 1. 14. An air conditioner using the blower according to claim 13.