Patent Description:
PTL <NUM> discloses an outer rotor type motor having a structure in which a rotor main body <NUM> is attached to a flange portion <NUM> integrally formed near a motor shaft <NUM> and an inner fan <NUM> is also integrally attached on the upper surface of a bottom portion <NUM> of the rotor main body <NUM>. PTL <NUM> and PTL <NUM> show a motor according to the preamble of claim <NUM>. PTL <NUM> and PTL <NUM> also show similar motors.

The structure disclosed in PTL <NUM>, however, has a problem that the centrifugal force (load) by a magnet <NUM> provided on the outer end side (the inner side of a tubular portion) of the rotor main body <NUM> acts on the flange portion <NUM> formed near the motor shaft, and thus the reliability in strength of the flange portion <NUM> may lower.

The present invention has as its object to provide an outer rotor type motor excellent in strength reliability.

The above-identified problems are solved by the independent patent claims of the invention. Respective dependent claims describe advantageous embodiments of the invention.

An outer rotor type motor according to an aspect of the present invention is an outer rotor type motor including a rotor in which magnets are arranged on an inner circumferential surface of a cylindrical rotor yoke. The outer rotor type motor comprises a motor shaft configured to rotatably support the rotor and a rotor attachment member including a base end extended from an outer periphery of the motor shaft outward in a radial direction and an outer end formed from an outer periphery of the base end outward in the radial direction. The outer end is formed at a position close to the inner circumferential surface of the rotor yoke, as compared with an outer peripheral surface of the motor shaft. The rotor is attached to the outer end. The base end is formed so that a thickness in an axial direction of the motor shaft gradually decreases from the outer periphery of the motor shaft to the outer end that is radially outside.

A step is formed between the base end and the outer end along the axial direction of the motor shaft, and the rotor is attached to the outer end in a state in which an opening of the rotor yoke is fitted in the step.

The cylindrical rotor yoke includes a connecting portion formed to overlap the outer end along a vertical direction intersecting the axial direction of the motor shaft, a tubular portion formed so as to arrange the magnets on the inner circumferential surface and a joint portion configured to join the connecting portion and the tubular portion via a plurality of bending portions that are formed between the connecting portion and the tubular portion.

The outer rotor type motor comprises a fan formed concentrically with the rotor yoke, and the fan is attached to the outer end in a state in which the rotor yoke is attached between the fan and the outer end.

Preferably, a first engaging portion of the outer rotor type motor is configured to be engaged with a yoke attachment member for attaching the rotor yoke and a second engaging portion configured to be engaged with a fan attachment member for attaching the fan is preferably formed along a same circumference in the outer end.

Preferably, in the outer rotor type motor a through hole through which the yoke attachment member passes and a through hole through which the fan attachment member passes is preferably formed along a same circumference in the rotor yoke.

In the outer rotor type motor according to the aspect, the cylindrical rotor yoke includes a blade portion of the fan is arranged in a space formed between the fan and the joint portion.

The joint portion preferably includes, as the plurality of bending portions, a first bending portion formed by bending the joint portion toward the tubular portion at a first angle formed between the connecting portion formed in the vertical direction with respect to the axial direction of the motor shaft and the tubular portion formed along the axial direction, and a second bending portion formed by bending, at a second angle, formed between the joint portion bent at the first angle and the tubular portion formed along the axial direction.

Preferably, a notch portion of the outer rotor type motor is formed not to abut against the yoke attachment member for attaching the rotor yoke to the outer end is formed in the fan.

Preferably, when a distance from a center of the motor shaft to a central portion of the outer end in the radial direction is set as a first distance, and a distance from the center of the motor shaft to an outer peripheral portion of the rotor yoke is set as a second distance, the outer end is attached at a position where a relation of the first distance > <NUM> × the second distance is satisfied.

According to the aspect of the present invention, it is possible to reduce the influence of the centrifugal force (load) that can be generated by the rotation of a rotor by forming an outer end attached with the rotor at a position close to the inner circumferential surface of a rotor yoke, as compared with the outer peripheral surface of the motor shaft, thereby providing an outer rotor type motor excellent in strength reliability.

Since the rotor attachment member includes the base end formed so that the thickness in the axial direction of the motor shaft gradually decreases toward the outer end that is radially outside, it is possible to distribute the load (stress concentration) that can locally occur in a portion on the fixed end side (a portion on the side of the motor shaft) of the base end by the rotation of the rotor while ensuring rigidity of a portion as a base of the outer end to which the rotor is attached.

By forming the outer end outward in the radial direction from the outer periphery of the base end formed so that the rigidity is ensured and stress concentration is prevented, it is possible to form the outer end at a position close to the inner circumferential surface of the cylindrical rotor yoke, as compared with the outer peripheral surface of the motor shaft. This can reduce the influence of the centrifugal force (load) that can be generated by the rotation of the rotor, thereby providing the outer rotor type motor excellent in strength reliability.

By faucet joining (mate fitting) using the step, positioning of the rotor and the rotor attachment member becomes easy, thereby making it possible to reduce an error of the shaft center at the time of assembly. In addition, since faucet joining can increase the contact area of the rotor yoke and the outer end and base end of the rotor attachment member, the load acting on the outer end while the rotor is attached can be distributed toward the base end.

In the outer rotor type motor according to the aspect, by providing the plurality of bending portions, it is possible to form a portion between the connecting portion and the tubular portion at an obtuse angle as a gentle bending angle in each bending portion. This can further relax the stress concentration in the rotor yoke, as compared with a case in which the portion between the connecting portion and the tubular portion bends at a right angle.

In the outer rotor type motor according to the aspect, by concentrically attaching the rotor yoke and the fan to the outer end of the rotor attachment member along a same circumference, it is unnecessary to additionally provide, in the outer end, the fan attachment portion as a structure for attaching the fan, thereby making it possible to decrease the size of the outer end (the dimension of the outer end in the radial direction).

In the outer rotor type motor according a preferred embodiment, in shape design of the rotor yoke, it is unnecessary to consider restrictions of the arrangement and sectional shape of the engaging portion for attaching the fan to the rotor yoke. For example, when the fan is attached to the rotor yoke, restrictions such as a restriction that a bottom portion needs to be formed by linearly extending the connecting portion of the rotor yoke in consideration of engagement with a fastening member can be imposed on the shape design.

With the structure in which the fan is attached to the outer end of the rotor attachment member, it is possible to improve the degree of freedom in the shape design of the rotor yoke. For example, it is possible to form the plurality of bending portions and between the connecting portion and the tubular portion like the sectional shape of the rotor yoke. This can form the rotor yoke in a shape that can relax the stress concentration.

In the outer rotor type motor according to the aspect, by arranging the blade portion in the space formed when the joint portion bends, the outer rotor type motor with the cooling mechanism (fan) using the rotation driving force of the motor can further be decreased in size.

In addition, when the joint portion bends by the plurality of bending portions , the space where the blade portion can be arranged can be enlarged, and it is possible to decrease the size, and also cool the outer rotor type motor using the fan with a larger area of the blade portion and improved cooling performance.

In the outer rotor type motor according to a preferred embodiment, while maintaining the state in which the rotor yoke is attached to the outer end of the rotor attachment member, it is possible to detach only the fan from the outer end of the rotor attachment member. This can improve the maintainability of the outer rotor type motor.

In the outer rotor type motor according to a preferred embodiment, by forming the outer end attached with the rotor at a position (the first distance > <NUM> × the second distance) close to the inner circumferential surface of the cylindrical rotor yoke, as compared with the outer peripheral surface of the motor shaft, it is possible to reduce the influence of the centrifugal force (load) that can be generated by the rotation of the rotor , thereby providing the outer rotor type motor excellent in strength reliability.

Other features and advantages of the present invention will be apparent from the following descriptions taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.

The constituent elements described in the embodiments are merely examples and are not limited by the following embodiments.

<FIG> is a sectional view showing the arrangement of an outer rotor type motor according to the first embodiment. As shown in <FIG>, an outer rotor type motor <NUM> is an outer rotor type motor including a rotor <NUM> in which a plurality of magnets <NUM> are arranged on the inner circumferential surface of a cylindrical rotor yoke <NUM>. A motor shaft <NUM> is rotatably supported by bearings <NUM> and <NUM> provided in a motor housing <NUM>. The plurality of magnets <NUM> arranged on the inner circumferential surface of the rotor yoke <NUM> are arranged to alternately form different magnetic poles in the circumferential direction.

In this embodiment, a rotor attachment member <NUM> is formed integrally with the motor shaft <NUM>. The rotor attachment member <NUM> includes a base end <NUM> extended from the outer periphery of the motor shaft <NUM> outward in a radial direction, and an outer end <NUM> formed from the outer periphery of the base end outward in the radial direction.

When a distance from the center of the motor shaft <NUM> to the central portion (yoke attachment members <NUM> to be described later) of the outer end <NUM> in the radial direction is set as the first distance (= D1/<NUM> = R1), and a distance from the center of the motor shaft <NUM> to the outer peripheral portion of the rotor yoke <NUM> is set as the second distance (= D2/<NUM> = R2), the outer end <NUM> is formed at a position where a relation of the first distance (R1) > <NUM> × the second distance (R2) is satisfied.

That is, the outer end <NUM> (yoke attachment members <NUM>) of the rotor attachment member <NUM> is formed at a position (first distance (R1) > <NUM> × second distance (R2)) close to the inner circumferential surface of the rotor yoke <NUM>, as compared with the outer peripheral surface (tubular portion <NUM>) of the motor shaft <NUM>, and the rotor <NUM> is attached to the outer end <NUM>. The motor shaft <NUM> rotatably supports the rotor <NUM>, and the rotor <NUM> attached to the outer end <NUM> is rotated by the rotation of the motor shaft <NUM>.

By forming the outer end <NUM> attached with the rotor <NUM> at a position close to the inner circumferential surface (tubular portion <NUM>) of the cylindrical rotor yoke <NUM>, as compared with the outer peripheral surface of the motor shaft <NUM>, it is possible to reduce the influence of the centrifugal force (load) that can be generated by the rotation of the rotor, thereby providing the outer rotor type motor excellent in strength reliability.

<FIG> is an enlarged view of the structure of the rotor attachment member <NUM> shown in an A portion in <FIG>. The member thickness (thickness) of the base end <NUM> on the side of the motor shaft <NUM> is represented by TH1, and the member thickness (thickness) of the base end <NUM> on the side of the outer end <NUM> extending outward in the radial direction is represented by TH2. The base end <NUM> is formed so that the thickness in the axial direction of the motor shaft <NUM> (to be simply referred to as an axial direction hereinafter) gradually decreases from the outer periphery of the motor shaft <NUM> to the outer end <NUM> that is radially outside. It is possible to distribute stress concentration that can locally occur in a portion on the fixed end side (a portion on the side of the motor shaft <NUM>) of the base end <NUM> by the rotation of the rotor <NUM> while ensuring rigidity of a portion as a base of the outer end <NUM> to which the rotor is attached.

By forming the outer end <NUM> outward in the radial direction from the outer periphery of the base end <NUM> formed so that the rigidity is ensured and stress concentration is prevented, it is possible to form the outer end <NUM> at a position close to the inner circumferential surface (tubular portion <NUM>) of the cylindrical rotor yoke <NUM>, as compared with the outer peripheral surface of the motor shaft <NUM>. This can reduce the influence of the centrifugal force (load) that can be generated by the rotation of the rotor <NUM>, thereby providing the outer rotor type motor excellent in strength reliability.

As shown in <FIG>, a step <NUM> having a different thickness is formed between the base end <NUM> and the outer end <NUM> along the axial direction of the motor shaft <NUM>. The rotor <NUM> is attached to the outer end <NUM> by the yoke attachment members <NUM> (for example, bolts) in a state in which the opening of the rotor yoke <NUM> is fitted in the step <NUM>. By faucet joining using the step <NUM>, positioning of the rotor <NUM> (rotor yoke <NUM>) and the rotor attachment member <NUM> becomes easy, thereby making it possible to reduce an error of the shaft center at the time of assembly. In addition, since faucet joining can increase the contact area of the rotor yoke <NUM> and the outer end <NUM> and base end <NUM> of the rotor attachment member <NUM>, the load acting on the outer end <NUM> while the rotor <NUM> is attached can be distributed toward the base end <NUM>.

Referring back to <FIG>, the sectional structure of the rotor yoke <NUM> will be described. The cylindrical rotor yoke <NUM> includes a connecting portion <NUM> formed to overlap the outer end <NUM>, the tubular portion <NUM> formed so as to arrange the magnets <NUM> on the inner circumferential surface, and a joint portion <NUM> that joins the connecting portion <NUM> and the tubular portion <NUM> via a plurality of bending portions formed between the connecting portion <NUM> and the tubular portion <NUM>.

A portion, contacting the connecting portion <NUM>, of the outer end <NUM> of the rotor attachment member <NUM> is formed in a planar shape in a direction (to also be referred to as a vertical direction hereinafter) intersecting the axial direction of the motor shaft <NUM>, and the connecting portion <NUM> of the rotor yoke <NUM> is formed along the vertical direction in a planar shape to overlap the outer end <NUM>. The tubular portion <NUM> of the rotor yoke <NUM> is formed in a cylindrical shape, and arranged so that the plurality of magnets <NUM> with different magnet poles formed alternately in the circumferential direction can be arranged.

In the example shown in <FIG>, a plurality of bending portions <NUM> and <NUM> are formed between the connecting portion <NUM> and the tubular portion <NUM>, and the joint portion <NUM> is formed to join the connecting portion <NUM> and the tubular portion <NUM> via the plurality of bending portions <NUM> and <NUM>. The joint portion <NUM> that includes the two bending portions <NUM> and <NUM> as the plurality of bending portions is exemplified. However, an example of the arrangement of the bending portions is not limited to this, and two or more bending portions can be formed.

The bending portion <NUM> (to also be referred to as the "first bending portion" hereinafter) is formed to bend the joint portion <NUM> toward the tubular portion <NUM> at a predetermined first angle (obtuse angle) between the connecting portion <NUM> formed in the vertical direction with respect to the axial direction of the motor shaft <NUM> and the tubular portion <NUM> formed along the axial direction of the motor shaft <NUM> (formed almost in parallel to the axial direction of the motor shaft <NUM>).

The bending portion <NUM> (to also be referred to as the "second bending portion" hereinafter) is formed to bend, at a predetermined second angle (obtuse angle), the joint portion <NUM> bending at the first angle (obtuse angle) by the bending portion <NUM> (first bending portion) to be joined to the tubular portion <NUM>.

In the bending portions <NUM> and <NUM>, the first and second angles are both obtuse angles, and can be set based on the shape design (the structure of the connecting portion <NUM>, the tubular portion <NUM>, and the like) of the rotor yoke <NUM>. That is, based on the structure of the connecting portion <NUM>, the tubular portion <NUM>, and the like, the first and second angles of the joint portion <NUM> can be set to the same angle, set so that the first angle is larger than the second angle, or set so that the first angle is smaller than the second angle. By connecting the connecting portion <NUM> and the tubular portion <NUM> by the joint portion <NUM>, the rotor yoke <NUM> is formed in such cylindrical shape that one opening of the tubular portion <NUM> is partially sealed.

Referring to <FIG>, a stator <NUM> includes a stator core including a core main body in an almost annular shape, and a plurality of coils wounded around the stator core, and is fixed to the inside of the motor housing <NUM> by a stator fastening member <NUM>. In the state in which the stator <NUM> is fixed to the inside of the motor housing <NUM>, the stator <NUM> and the magnets <NUM> arranged on the inner circumferential surface of the tubular portion <NUM> face each other.

The coils of the stator <NUM> are supplied with a driving current from an external motor control apparatus (not shown) via a cable <NUM> and an electrical connection portion <NUM>, and the rotor <NUM> is rotated by a magnetic field generated by the driving current. Rotation information of the motor shaft <NUM> detected by a rotation detection element (not shown) is configured to be transmittable to an external control apparatus.

<FIG> is a view schematically showing a state in which the rotor yoke <NUM> is attached to the outer end <NUM> of the rotor attachment member <NUM>. In the rotor yoke <NUM>, through holes 39B through which the yoke attachment members <NUM> (for example, bolts) pass are formed. Each of the through holes 39B is formed to have a hole diameter larger than the diameter (screw diameter) of the yoke attachment member <NUM>. The yoke attachment members <NUM> are engaged with first engaging portions 29B (screw holes) formed in the outer end <NUM> to attach the rotor yoke <NUM> to the outer end <NUM>.

In <FIG>, ST81 shows a state in which the rotor attachment member <NUM> (base end <NUM> and outer end <NUM>) formed in the motor shaft <NUM> is viewed from a direction of an arrow <NUM> in <FIG>. In the outer end <NUM>, the first engaging portions 29B (screw holes) that can be engaged with the yoke attachment members <NUM> for attaching the rotor yoke <NUM> (rotor <NUM>) and second engaging portions 29A (screw holes) that can be engaged with fan attachment members <NUM> for attaching a fan <NUM> are formed along a same circumference.

By concentrically attaching the rotor yoke <NUM> and the fan <NUM> to the outer end <NUM> of the rotor attachment member <NUM>, that is, attaching the rotor yoke <NUM> and the fan <NUM> using the outer end <NUM> formed in a planar and annular shape, it is unnecessary to additionally provide, in the outer end <NUM>, a fan attachment portion as a structure for attaching the fan <NUM>, thereby making it possible to decrease the size of the outer end <NUM> (the dimension of the outer end <NUM> in the radial direction).

In <FIG>, ST82 shows a state in which a state of attaching the rotor yoke <NUM> to the outer end <NUM> is viewed from the direction of the arrow <NUM> in <FIG>. An opening 32B is formed at the center of the rotor yoke <NUM>, and the rotor yoke <NUM> (rotor <NUM>) is attached to the outer end <NUM> in a state in which the step <NUM> (<FIG>) is fitted in the opening 32B. In ST82 of <FIG>, through holes 39A are formed so that the fan attachment members <NUM> for attaching the fan <NUM> to the outer end <NUM> pass through the rotor yoke <NUM>. In the rotor yoke <NUM>, the through holes 39B (<FIG>) through which the yoke attachment members <NUM> pass and the through holes 39A through which the fan attachment members <NUM> pass are formed along a same circumference. Similar to the through holes 39B, each of the through holes 39A is formed to have a hole diameter larger than the diameter (screw diameter) of the fan attachment member <NUM>.

The outer rotor type motor <NUM> includes a fan <NUM> (external fan) and the fan <NUM> (internal fan) as a cooling mechanism using the rotation driving force of the motor.

The fan <NUM> (external fan) is attached to the motor shaft <NUM> by a fastening member such as a key. The fan <NUM> (internal fan) is formed concentrically with the rotor yoke <NUM>. In a state in which the rotor yoke <NUM> is attached between the fan <NUM> and the outer end <NUM>, the fan <NUM> is attached to the outer end <NUM>. The fan <NUM> is attached to the outer end <NUM> by the fan attachment members <NUM> such as bolts.

On the side of the outer rotor type motor <NUM>, a motor cover <NUM> is attached to the motor housing <NUM> by a cover fastening member <NUM> (for example, a bolt or the like), and the fan <NUM> (external fan) is covered with the motor cover <NUM>.

When the fan <NUM> (internal fan) and the fan <NUM> (external fan) turn by the rotation of the motor shaft <NUM>, the fan <NUM> (internal fan) circulates air in the outer rotor type motor <NUM>, thereby cooling the rotor <NUM>, the stator <NUM>, and the like.

Furthermore, the fan <NUM> (external fan) sends, toward the outer wall (motor housing <NUM>) of the outer rotor type motor <NUM>, air taken from an intake opening (not shown) formed in the motor cover <NUM>, thereby cooling the outer wall of the outer rotor type motor <NUM>. Air (external cooling air) sent by the fan <NUM> (external fan) cools the outer wall of the motor <NUM>, and also encourages heat exchange between the outer wall and internally circulating air by the fan <NUM> (internal fan).

<FIG> is a view schematically showing a state in which the fan <NUM> is attached to the outer end <NUM> of the rotor attachment member <NUM>. In the rotor yoke <NUM> arranged between the outer end <NUM> and the fan <NUM>, the through holes 39A through which the fan attachment members <NUM> (for example, bolts) pass are formed. The fan <NUM> is attached to the outer end <NUM> when the fan attachment members <NUM> are engaged with the second engaging portions 29A (screw holes: <FIG>) formed in the outer end <NUM>.

In <FIG>, ST61 shows a state in which the fan <NUM> attached to the outer end <NUM> is viewed from a direction of an arrow <NUM> in <FIG>. In <FIG>, ST62 shows a state in which only the fan <NUM> is viewed from the direction of the arrow <NUM> in <FIG>. Through holes <NUM> through which the fan attachment members <NUM> pass are formed in the fan <NUM>. Similar to the through holes 39A, each of the through holes <NUM> is formed to have a hole diameter larger than the diameter (screw diameter) of the fan attachment member <NUM>. In addition, notch portions <NUM> are formed to be larger than the outer diameters of the yoke attachment members <NUM> in the fan <NUM> so as not to abut against the yoke attachment members <NUM> for attaching the rotor yoke <NUM> to the outer end <NUM>.

As shown in ST61 of <FIG>, in a state in which the rotor yoke <NUM> is attached to the outer end <NUM> by the yoke attachment members <NUM>, the fan <NUM> is also attached to the outer end <NUM> by the fan attachment members <NUM>. In the state in which the fan <NUM> is attached to the outer end <NUM>, the notch portions <NUM> prevent the yoke attachment members <NUM> and the fan <NUM> from abutting against each other.

Since the yoke attachment members <NUM> and the fan <NUM> do not abut against each other, if the fan attachment members <NUM> are removed in the state in which the rotor yoke <NUM> is attached, only the fan <NUM> can be detached from the outer end <NUM>. That is, while maintaining the state in which the rotor yoke <NUM> (rotor <NUM>) is attached to the outer end <NUM> of the rotor attachment member <NUM>, it is possible to detach only the fan <NUM> from the outer end <NUM> of the rotor attachment member <NUM>. This can improve the maintainability of the outer rotor type motor.

As shown in <FIG>, the fan <NUM> includes a fan main body <NUM> and a plurality of blade portions <NUM> arranged in the circumferential direction. In the state in which the fan <NUM> is attached to the outer end <NUM>, the blade portions <NUM> of the fan <NUM> are arranged in a space formed between the fan main body <NUM> and the joint portion <NUM> bending by the plurality of bending portions <NUM> and <NUM>.

For example, if no bending portions are provided in the joint portion <NUM> and the connecting portion <NUM> is extended linearly in the vertical direction, the space between the joint portion and the fan main body <NUM> is small, and the sizes of the blade portions of the fan are limited. If each blade portion is formed in a size equal to that of the blade portion <NUM> shown in <FIG>, the attachment position of the fan <NUM> shifts in the right direction on the drawing surface of <FIG> along the axial direction of the motor shaft <NUM>, and the cooling mechanism increases in size.

By arranging the blade portions <NUM> in the space formed when the joint portion <NUM> bends by the plurality of bending portions <NUM> and <NUM>, the outer rotor type motor <NUM> with the cooling mechanism using the rotation driving force of the motor can further be decreased in size. In addition, when the joint portion <NUM> bends by the plurality of bending portions <NUM> and <NUM>, the space where the blade portions <NUM> can be arranged can be enlarged, as shown in <FIG>, and it is possible to decrease the size, and also cool the outer rotor type motor <NUM> using the fan <NUM> with a larger area of the blade portions <NUM> and improved cooling performance.

<FIG> is a sectional view showing the arrangement of an outer rotor type motor <NUM> according to the second embodiment. The first embodiment has explained an example in which the fan <NUM> (external fan) and the fan <NUM> (internal fan) are arranged at one end of the motor shaft <NUM> as the cooling mechanism of the outer rotor type motor <NUM>. The present invention, however, is not limited to this. As shown in <FIG>, a fan <NUM> (external fan) can be arranged at one end of a motor shaft <NUM> and a fan <NUM> (internal fan) can be arranged at the other end of the motor shaft <NUM>. In this case, the arrangement direction of a rotor attachment member <NUM> and a rotor <NUM> is opposite to that in <FIG>. However, in this embodiment as well, it is possible to obtain the same effect as in the outer rotor type motor <NUM> according to the first embodiment.

<FIG> is a sectional view showing the arrangement of an outer rotor type motor <NUM> according to the third embodiment. Each of the first and second embodiments has explained an example of the arrangement of the outer rotor type motor <NUM> in which the rotor attachment member <NUM> is integrally formed with the motor shaft <NUM> by, for example, casting or cutting. However, a rotor attachment member <NUM> and a motor shaft <NUM> can be formed as separate parts.

In this case, for example, as shown in <FIG>, a tapered portion 11A is provided in the motor shaft <NUM>, an engaging hole 11B that is engaged with the tapered portion 11A is formed on the side of the rotor attachment member <NUM>, and the rotor attachment member <NUM> is positioned at a predetermined position on the motor shaft <NUM> by the tapered portion 11A and the engaging hole 11B.

In the example shown in <FIG>, a fan <NUM> (external fan) is arranged at one end of the motor shaft <NUM> and a fan <NUM> (internal fan) is arranged at the other end of the motor shaft <NUM>. However, as shown in <FIG>, the fan <NUM> (external fan) and the fan <NUM> (internal fan) may be arranged at one end of the motor shaft <NUM>. In this embodiment as well, it is possible to obtain the same effect as in the outer rotor type motor <NUM> according to the first embodiment.

The present invention is not limited to the above embodiments and various changes and modifications can be made within the scope of the present invention as defined by the appended claims.

Claim 1:
An outer rotor type motor (<NUM>) including a rotor (<NUM>) in which magnets (<NUM>) are arranged on an inner circumferential surface of a cylindrical rotor yoke (<NUM>), comprising:
a motor shaft (<NUM>) configured to rotatably support the rotor (<NUM>); and
a rotor attachment member (<NUM>) including a base end (<NUM>) extended from an outer periphery of the motor shaft (<NUM>) outward in a radial direction and an outer end (<NUM>) formed from an outer periphery of the base end (<NUM>) outward in the radial direction,
wherein
the outer end (<NUM>) is formed at a position close to the inner circumferential surface of the rotor yoke (<NUM>), as compared with an outer peripheral surface of the motor shaft (<NUM>),
the rotor (<NUM>) is attached to the outer end(<NUM>),
the base end (<NUM>) is formed so that a thickness in an axial direction of the motor shaft (<NUM>) gradually decreases from the outer periphery of the motor shaft (<NUM>) to the outer end (<NUM>) that is radially outside,
a step (<NUM>) is formed between the base end (<NUM>) and the outer end (<NUM>) along the axial direction of the motor shaft (<NUM>),
the rotor (<NUM>) is attached to the outer end (<NUM>) in a state in which an opening of the rotor yoke (<NUM>) is fitted in the step (<NUM>),
the outer rotor type motor (<NUM>) further comprising a fan (<NUM>) formed concentrically with the rotor yoke (<NUM>),
wherein the fan (<NUM>) is attached to the outer end (<NUM>) in a state in which the rotor yoke (<NUM>) is attached between the fan (<NUM>) and the outer end (<NUM>), and wherein the cylindrical rotor yoke (<NUM>) includes
a connecting portion (<NUM>) formed to overlap the outer end (<NUM>) along the radial direction of the motor shaft (<NUM>),
a tubular portion (<NUM>) formed so as to arrange the magnets (<NUM>) on the inner circumferential surface, and
a joint portion (<NUM>) configured to join the connecting portion (<NUM>) and the tubular portion (<NUM>) via a plurality of bending portions (<NUM>, <NUM>) formed between the connecting portion (<NUM>) and the tubular portion (<NUM>), and
a blade portion (<NUM>) of the fan (<NUM>) is arranged in a space formed between the fan (<NUM>) and the joint portion (<NUM>).