JPH07222421A - Brushless motor - Google Patents

Abstract

PURPOSE:To obtain the brushless motor in which the use of an adhesive is excluded by a method wherein, at a stator stack, a bend part whose cross section in the radial direction has been bent to be L-shaped in a part faced with a rotor magnet is formed and its tip part is welded and fixed to a stationary member. CONSTITUTION:A stator stack 10 is formed in such a way that the prescribed number of plates formed by making a ferromagnetic-substance material such as an electromagnetic steel plate or the like to be a thin shape are laminated, and the required number of protrusion-shaped magnetic poles which are installed at equal intervals to the same direction are formed on the side of a rotor magnet. In addition, an upper-end plate 12 and a lowerend plate 13 are bent respectively on the side of the rotor magnet 4 in such a way that their cross section in the radial direction is L-shaped. The plate 12 on the upper side has a bend part 14 which is bent to the upward direction, and the plate 13 on the lower side has a bend part 15 which is bent to the downward direction. Then, the bend part 15 is formed in such a way that its tip part is slightly long as compared with the bend part 15. The tip part 17 is inserted into, and buried in, a hole part 16 which is bored in a bracket 6, and it is fixed by a welding operation. As a result, the tip part can be fixed surely and easily without using an adhesive.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor having a ferrous core stator around which a drive winding is wound.

[0002]

2. Description of the Related Art There is a brushless motor provided with a stator having an iron core around which a drive winding is wound, and a rotor magnet which is arranged opposite to the stator and which obtains a rotational driving force by interaction with the stator. Generally, the iron core of the stator is formed by laminating a required number of thin plates made of a ferromagnetic material. In addition, a protruding portion (tooth portion) around which the winding is wound is provided in a portion facing the rotor magnet in correspondence with the required number of magnetic poles.

A so-called radial gap type brushless motor, in which a stator and a rotor magnet are arranged so as to face each other with a gap in the radial direction with respect to a rotation axis, is disclosed in, for example, Japanese Patent Laid-Open No. 5-316703 and Japanese Utility Model Publication No.
-70184 gazette etc. are disclosed. The stator is
It is received by a stepped portion provided on the outer peripheral side of the bearing cylindrical portion in the housing (bracket), and is externally fitted and held. In general, an adhesive is used to fix the stator and the housing.

[0004]

By the way, various OA devices and the like in which such a brushless motor is incorporated are becoming smaller and lighter in recent years, and the internal parts including the motor are correspondingly downsized. , Downsizing is needed. On the other hand, a high driving force is required, so that it is necessary to provide a highly efficient motor. However, according to the brushless motor having the above-described structure, the following problems are posed in order to reduce the thickness and increase the efficiency while ensuring the magnetic space between the rotor magnet and the stator arranged to face the rotor magnet. Have a point.

Particularly, on the stator side, in addition to the shape space such as the thickness of the iron core itself, the space for the winding wound around the iron core is included. As a result, even if the iron core is made to correspond to the required shape in order to reduce the thickness, a large amount of space is required for the winding wound around the iron core, and there is a limit to the reduction in thickness. Moreover, in such a configuration, it cannot be said that the magnetic space is effectively used to improve the efficiency. If the balance is lost, it may cause an increase in electromagnetic vibration and a rise in temperature. As described above, some measures have been desired in order to reduce the size and increase the efficiency of the brushless motor.

Further, the stator and the housing have been conventionally fixed by using an adhesive, but with the miniaturization of the motor, the application site becomes relatively small and application becomes difficult, and at the same time, the application becomes difficult. Management of the coating amount also becomes complicated. This not only causes uncured adhesive and uneven coating, but a sufficient adhesive force cannot be obtained, and various inconveniences are caused by the gas remaining in the adhesive.

The present invention has been made in view of the above problems existing in the prior art, and its object is to make the magnetic space of the rotor magnet and the stator effective. It is an object of the present invention to provide a brushless motor that can be made smaller, thinner, and more efficient. Another object of the present invention is to provide a brushless motor which can be easily manufactured and can be securely fixed to the stator and the housing without using an adhesive, thereby improving productivity and reliability. It is to be.

[0008]

In order to achieve the above object, a brushless motor according to the present invention comprises a stationary member, a rotating member which is rotatably supported relative to the stationary member, and a thin member made of a ferromagnetic material. A rotating force is generated by electromagnetic interaction between a stator stack in which a required number of plates are laminated and a stator coil wound around this stator stack to generate a current magnetic field in an excited state, and electromagnetic current of the stator coil. A brushless motor including a rotor magnet to be obtained; a plate at a laminated end portion of the stator stack is provided with a bent portion that is bent in an L-shaped radial cross section at a portion facing the rotor magnet. There is provided a brushless motor in which a tip end of the portion is embedded in the stationary member and fixed by welding.

[0009]

According to the brushless motor of the present invention, the plate at the laminated end of the stator stack is provided with a bent portion bent in an L-shaped radial cross section at a portion facing the rotor magnet. The L-shaped bent portion is arranged to face the rotor magnet at a substantially constant interval, and the lamination thickness dimension of the stator stack increases by this amount. Therefore, the magnetic pole area of the stator facing the rotor magnet is increased, and the magnetic path between the rotor magnet and the stator is expanded. As a result, the magnetic coupling between the rotor magnet and the stator becomes close,
The efficiency is improved, and the laminated thickness of the stator stack can be reduced.

Further, since the tip end of the bent portion of the stator stack is embedded in the stationary member and fixed by welding, it can be easily fixed and reliable fixed without using a fixing member such as an adhesive. . Moreover, since the fixed portion of the stator is on the rotor magnet side, the stator is fixed at the portion where the electromagnetic vibration is the largest, so that this vibration can be reduced as much as possible.

[0011]

Embodiments of the brushless motor according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing a brushless motor for rotating a recording disk, for example, and showing the whole thereof. In FIG. 1, a member 6 is a shallow plate-shaped bracket, and an overhanging portion 30 projecting in the outer peripheral direction is attached and fixed to a disk drive device (not shown). The bracket 6 may be the base member of the disk drive device itself. A hole 36 is formed in the center of the bracket 6, and the lower end of the shaft 2 is fitted and fixed in the hole 36. The bracket 6 is formed by using a non-magnetic material such as an aluminum alloy.

The shaft 2 has a substantially cylindrical shape, and on the lower side of the figure, a thrust plate 9 which is provided so as to project annularly is integrally provided. The thrust plate 9 is
It is formed substantially perpendicular to the shaft 2. The upper and lower end surfaces 25, 40 are defined to be substantially parallel to each other. Lower end surface 40 of thrust plate 9
Is positioned to define the height and verticality with respect to the bottom wall 31 of the bracket 6, and the upper end surface 25 has a herringbone-shaped dynamic pressure groove (groove, not shown) at a constant interval in the circumferential direction. ) Is engraved. Herringbone-shaped dynamic pressure grooves (grooves) 19 are engraved in the outer peripheral portion 20 of the shaft 2 at regular intervals in the circumferential direction at a substantially central portion thereof. The shaft 2 is made of, for example, stainless steel. The shaft 2 and the bracket 6 form a stationary member of the brushless motor of the present invention.

A rotating member (rotor) 1 which is rotatably supported with respect to the stationary member includes a hub 5 having an inverted cup shape and a sleeve 8 having a substantially cylindrical shape. The hub 5 is made of, for example, stainless steel made of a ferromagnetic material,
The central part is formed in a hollow shape. Outer peripheral wall 38 of hub 5
Recording disks (not shown) are externally fitted to the outer peripheral portion 29, and are received by the collar portion 28 so that the required number of sheets are stacked in the upward direction of the drawing. On the inner peripheral side of the outer peripheral wall 38, the rotor magnet 4 which is magnetized as required is annularly arranged. The rotor magnet 4 has an outer peripheral wall 38.
It is positioned and fixed in the height (vertical direction in the figure) by a step portion 35 provided on the. The inner peripheral wall 37 of the hub 5 is formed in an annular shape and is provided so as to hang downward from the top of the drawing.

In the sleeve 8 integrally fixed to the hub 5 coaxially, the outer peripheral portion 41 (of the sleeve 8) is externally fitted and fixed to the inner side of the inner peripheral wall 37 (of the hub 5). And sleeve 8
The inner peripheral portion 24 has a cylindrical surface shape (inner peripheral portion), and is fitted in correspondence with the cylindrical surface shape (outer peripheral portion) of the outer peripheral portion 20 of the shaft 2. The lower end surface 26 of the sleeve 8 is received and held by the upper end surface 25 of the thrust plate 9. The sleeve 8 is made of, for example, lead bronze. A cover plate 7 is fixed to the upper end of the shaft 2 so as to straddle the hub 5 and the sleeve 8, and thus the upper portion of the hub 5 is covered.

A lubricating fluid such as oil is provided between the outer peripheral portion 20 of the shaft 2 and the inner peripheral portion 24 of the sleeve 8 which is fitted around the shaft 2 and surrounds the shaft 2. The radial dynamic pressure bearing is configured by the relative rotation between the sleeve 8 and the sleeve 8. Similar oil is also provided between the lower end surface 26 of the sleeve 8 and the upper end surface 25 of the thrust plate 9, and the thrust that lifts the sleeve 8 upward in the drawing by relative rotation of these oils. A dynamic pressure bearing is constructed. The hub 5 is rotatably supported on the shaft 2 by these dynamic pressure bearings.

In the drawing, the lower end surface 2 of the sleeve 8 is shown.
6 and the upper end surface 25 of the thrust plate 9 facing this are provided with small grooves facing each other. This small groove is formed in an annular shape, and a void 27 is formed in this groove. An oil repellent that repels the oil is applied to the gap 27 so that the oil does not leak to the outside due to the surface tension. Also, the upper end portion 21 of the sleeve 8
Also, the groove 22 is provided in an annular shape and the oil repellent is applied. Similarly, oil is prevented from leaking out between the upper end portion 21 of the sleeve 8 and the cover plate 7.

As the dynamic pressure bearing, dynamic pressure generating grooves for generating dynamic pressure are formed on the surface of the shaft 2 side. On the contrary, the opposite side of the inner peripheral portion 24 of the sleeve 8 ( A dynamic pressure groove may be provided on the radial dynamic pressure generation side) and on the lower end surface 26 side of the sleeve 8 (thrust dynamic pressure generation side).

The bottom wall 31 of the bracket 6 has a stator 3
Is fixed. The stator 3 is the stator stack 10
And a coil 11 wound around this. The stator stack 10 is formed by laminating a predetermined number of thin plates of ferromagnetic material such as electromagnetic steel plates. On the rotor magnet side of the stator stack 10, a required number of projecting magnetic poles, which are not shown, are provided at equal intervals in the circumferential direction. Of the plates forming the stator stack 10, the upper and lower end plates 1
On the rotor magnet 4 side, the reference numerals 2 and 13 are each bent in an L-shaped cross section in the radial direction.

The upper plate 12 has a bent portion 14 bent upward in the drawing, and the lower plate 13 has a bent portion 15 bent downward in the drawing. And
The geometric center of the outer periphery 33 of the stator stack 10,
The geometric center of the inner peripheral portion 34 of the rotor magnet 4 is
They are arranged so as to face each other in the direction of the axis of rotation (vertical direction in the figure) with a constant interval. That is, as is apparent from the drawing, the bent portion 15 is formed such that the tip end thereof is slightly longer than the bent portion 14. This is the bent portion 15 located on the lower side.
Since the front end portion 17 of the is embedded in the bracket 6, it is set to be longer by the embedded amount.

Bending portions 14 and 15 of the stator stack 10
Are formed for each magnetic pole in correspondence with the number of projecting magnetic poles. Due to the configuration of the bent portions 14 and 15, the magnetic path of the stator stack 10 to the rotor magnet 4 is substantially increased, so that the efficiency of the motor is improved. Therefore, the lamination thickness of the stator stack 10 can be reduced to be thin, and a highly efficient brushless motor can be obtained.

The stator 3 is attached to the bracket 6 as follows. A hole 16 is formed in a corresponding portion of the bracket 6 to which the stator 3 is attached. The hole 16 is provided in a shape of a long hole in the circumferential direction of the bracket 6, corresponding to each magnetic pole of the stator stack 10. The tip portion 17 of the bent portion 15 (of the lower plate 13) is inserted and embedded in the hole portion 16. The buried portion is fixed by welding such as spot welding.

For this reason, the bent end portion 17 of the stator stack 10 and the hole portion 16 of the bracket 6 are made to correspond to predetermined positions in advance, whereby the stator stack 1
0 can be easily positioned and attached to the bracket 6, and can be securely fixed without using an adhesive.

The inner peripheral side of the stator stack 10 is mounted on an annular protrusion 18 provided on the bracket 6. In this way, the stator 3 is supported and fixed to the bracket 6 on the inner peripheral side and the outer peripheral side, so that stable mounting is performed. Since the stator 3 is also held and fixed on the side of the rotor magnet 4 where electromagnetic vibration is particularly high, vibration is suppressed. The tip portion 17 of the bent portion 15 is
Since it is fixed to the bracket 6 made of a non-magnetic material, the problem that the magnetic path is closed under the stator 3 separately from the rotor magnet 4 side does not occur.

The coil lead wire drawn from the stator 3 is electrically connected to a printed circuit board 32 attached to the upper surface of the bottom wall 31 of the bracket 6, and the printed circuit board 32 is led out of the motor. When a required electric signal is applied to the printed circuit board 32, the stator 3
Is excited and a current magnetic field is generated. The hub 5 is rotationally driven by the electromagnetic interaction between the current magnetic field and the rotor magnet 4.

At this time, the hub 5 is rotatably supported with respect to the bracket 6 by the above-mentioned dynamic pressure radial and thrust bearings, but the magnetic center of the rotor magnet 4 and the magnetic center of the stator 3 are aligned with the rotation axis. It is slightly offset in the direction (vertical direction in the figure). That is, the magnetic center of the rotor magnet 4 is set to be above the magnetic center of the stator 3 in the figure. As a result, the hub 5 exerts a suction force acting on the bracket 6 from the upper side to the lower side in the drawing, and the hub 5 is prevented from easily coming off the bracket 6.

As described above, in the first embodiment, the stator 3
In the stator stack 10 of No. 3, bent portions 14 and 15 having an L-shaped cross section in the radial direction are provided on the upper and lower plates.
As a result, the bent portions 14 and 15 are arranged to face the rotor magnet 4 substantially at a constant interval in the rotation axis direction (vertical direction in the drawing), and the laminated thickness dimension of the stator stack 10 increases substantially. For this reason, the magnetic pole area of the stator 3 facing the rotor magnet 4 is increased, the magnetic path between the rotor magnet 4 and the stator 3 is expanded, and the magnetic coupling is made dense. Therefore, the efficiency is improved, and the thinning and miniaturization are achieved. Can be achieved.

The bent portion 1 of the stator stack 10
5 (the front end portion 17 thereof) also serves as a mounting foot for holding and fixing the stator 3 to the bracket 6, so that the mounting can be easily performed and stable fixing can be performed. Since this fixing is realized by welding, the fixing can be performed more easily and surely, and the manufacturing cost can be reduced. In addition, since no adhesive is used, uneven application and trouble of application are not required, and accidents related to uncured and the like do not occur.

Next, FIG. 2 is an overall sectional view showing a brushless motor of the second embodiment. In this embodiment, the first
Only parts and configurations different from those of the embodiment will be described, and description of overlapping parts will be omitted. In the first embodiment, the shaft 2 is fixed to the bracket 6 to serve as a stationary member (shaft fixed type), but in the second embodiment, the shaft 102 is attached to the hub 105 constituting the rotating body (rotor) 101. Are integrally formed (shaft rotation type).
Further, in the first embodiment, the sleeve 8 is provided on the rotating side, but in the second embodiment, the sleeve 108 that rotates relative to the shaft 102 is provided on the stationary member side of the bracket 106.

Further, in the first embodiment, the rotor magnet 4 is arranged outside the stator 3 (outer rotor type), whereas in the second embodiment, the stator 103 is provided.
The rotor magnet 104 facing the
That is, it is positioned on the inner circumference side (inner rotor type).

Further, in the second embodiment, the mounting structure of the stator 103 to the bracket 106 is different. This point will be described below. In the stator stack 110, the lower plate 113 is provided with bent portions 115 and 118 on both inner and outer circumferences (left and right in the drawing) in the circumferential direction. Of these, the bent portion 115 on the side facing the rotor magnet 104 has the role of expanding the magnetic pole, as in the first embodiment, and the stator stack 110 is attached to the bracket 106.
Make a mounting foot to be fixed to. The bent portion 118 forms the other mounting leg that fixes the stator stack 110 to the bracket 106. In the first embodiment, the bracket 6 is provided with the annular protruding portion 18, but in the second embodiment, the bent portion 118 plays the role.

Therefore, also in the second embodiment, the function and effect are the same as those in the first embodiment, and the description thereof will be omitted. The embodiment of the brushless motor according to the present invention has been described above, but any design changes or modifications can be made without departing from the spirit of the present invention. Further, the combinations and changes of the configurations shown in the first and second embodiments can be freely selected, and other various forms and quantities shown in this embodiment can be freely selected.

[0032]

Since the brushless motor of the present invention has the above-mentioned structure, it has the following effects. That is, according to the brushless motor of the present invention, the plate at the laminated end portion of the stator stack is bent at a portion facing the rotor magnet to have an L-shaped cross section in the radial direction. For this reason, the bent portion is arranged to face the rotor magnet with a substantially constant gap, and the laminated thickness dimension of the stator stack is increased by this amount, so that the magnetic coupling between the rotor magnet and the stator becomes more dense. . Therefore, efficiency is improved and the motor can be made thinner.

Further, since the tip of the bent portion of the stator stack is embedded in a stationary member such as a bracket and fixed by welding, the fixing member can be securely and easily fixed without requiring a fixing member such as an adhesive. . Moreover, since the fixed portion of the stator is on the rotor magnet side, it is fixed at the portion where the electromagnetic vibration is the largest, so this vibration can be reduced as much as possible.

As described above, a brushless motor which can be reduced in size and thickness and increased in efficiency, easy to manufacture, and highly reliable can be obtained.

[Brief description of drawings]

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

FIG. 2 is a cross-sectional view showing an entire brushless motor according to a second embodiment of the present invention.

[Explanation of symbols]

 1 rotor 2 shaft 3 stator 4 rotor magnet 5 hub 6 bracket 7 cover plate 8 sleeve

Claims (1)

[Claims] 1. A stationary member, a rotating member which is rotatably supported relative to the stationary member, a stator stack in which a required number of thin plates made of a ferromagnetic material are stacked, and an excited state which is wound around the stator stack. In a brushless motor comprising a stator composed of a stator coil for generating a current magnetic field and a rotor magnet for obtaining a rotational force by electromagnetic interaction with the current magnetic field of the stator coil, a plate at a laminated end of the stator stack. Is provided with a bent portion bent in an L-shaped radial cross section at a portion facing the rotor magnet, and a tip portion of the bent portion is embedded in the stationary member and fixed by welding. And brushless motor.