JP3437865B2 - Brushless motor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor having an iron core stator on which a driving winding is wound. 2. Description of the Related Art There is a brushless motor including a cored stator having a driving winding wound thereon, and a rotor magnet disposed opposite to the stator and obtaining a rotational driving force by interaction with the stator. Generally, the stator core is formed by laminating a required number of thin plates made of a ferromagnetic material. A protruding portion (teeth portion) around which the winding is wound is provided in a portion facing the rotor magnet in accordance with a required number of magnetic poles. A so-called radial gap type brushless motor in which a stator and a rotor magnet are arranged to face each other with a gap in a radial direction with respect to a rotation axis is disclosed in, for example, Japanese Patent Laid-Open Publication No.
-70184. 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), fitted and held outside. In general, the stator and the housing are fixed using an adhesive. [0004] By the way, various OA equipments and the like in which such a brushless motor is incorporated have recently been reduced in size and weight, and accordingly, internal parts including the motor have also been reduced in size. To respond, downsizing is required. On the other hand, a high driving force is required, and thus a need has arisen to provide a highly efficient motor. However, according to the brushless motor having the above-described structure, the following problems arise in securing a magnetic space between the rotor magnet and the stator disposed to face the rotor magnet while reducing the thickness and increasing the efficiency. Have a point. [0005] In particular, on the stator side, in addition to the shape space such as the thickness dimension of the iron core itself, a space for the winding wound around the iron core is included. As a result, even if the iron core is made to correspond to a required shape in order to reduce the thickness, a large space is required for the winding wound around the core, which limits the thickness reduction. Moreover, it cannot be said that such a configuration effectively uses the magnetic space to increase the efficiency. An imbalance may cause an increase in electromagnetic vibration, an increase in temperature, and the like. As described above, some measures have been desired to reduce the size and increase the efficiency of the brushless motor. Further, the stator and the housing are conventionally fixed by using an adhesive. However, as the size of the motor is reduced, the application area becomes relatively small, and the application becomes difficult. The management of the application amount is also complicated. As a result, uncured adhesive and uneven application of the adhesive are caused, and not only a sufficient adhesive force cannot be obtained, but also various inconveniences are caused by gas remaining in the adhesive. SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in the prior art, and an object thereof is to make effective use of a magnetic space by a rotor magnet and a stator. Another object of the present invention is to provide a brushless motor capable of realizing a small size and a low profile and high efficiency. Another object of the present invention is to provide a brushless motor which can be easily manufactured and can be securely fixed without using an adhesive between a stator and a housing and which can improve 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 rotatably supported relative to the stationary member, and a ferromagnetic material. A stator stack comprising a required number of thin plates laminated and a stator coil wound around the stator stack and generating a current magnetic field in an excited state, and an electromagnetic interaction between the stator coil and the current magnetic field. Allocated to the rotating member to obtain torque
A brushless motor having a rotor magnet provided; wherein the rotating member comprises a radial dynamic pressure bearing and the rotor magnet;
Acts in a direction to lift the rotating member from the stationary member
And a thrust hydrodynamic bearing.
Is lifting, wherein the plate stack end of the stator stack, the bent portion that is bent radially L-shaped cross section is provided at the rotor magnet facing the site, the tip is the stationary member of the bent portion When is embedded Ru fixed by welding to the
In both cases, the rotating member includes the stator and the rotor magnet.
The thrust motion is caused by the magnetic force acting between
A brushless motor is provided that is biased in a direction opposite to the direction of operation of the pressure bearing . 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 having a L-shaped cross section in the radial direction at a portion facing the rotor magnet. I have. The L-shaped bent portion is opposed to the rotor magnet at a substantially constant interval, and the laminated thickness of the stator stack increases by that much. Therefore, the magnetic pole area of the stator facing the rotor magnet increases, 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 tight,
Efficiency is enhanced, and the stack thickness of the stator stack can be reduced. [0010] Further, since the tip of the bent portion of the stator stack is buried in the stationary member and fixed by welding, it can be easily fixed without using a fixing member such as an adhesive and can be reliably fixed. . In addition, since the fixed portion of the stator is on the rotor magnet side, it is fixed at a portion where the electromagnetic vibration is largest, so that the vibration can be reduced as much as possible. in addition,
A bent portion is provided on the plate at the end of the stack of the stator stack.
By doing so, the magnetic center of the stator and the rotor magnet
The magnetic center of the net is slightly displaced in the axial direction,
Axial magnetic force acts on rotating members
Therefore, the detachment of the rotating member is prevented. An embodiment of a brushless motor according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing the entirety of a brushless motor for rotating a recording disk, for example. In FIG. 1, a member 6 is a bracket having a shallow dish shape, and a projecting portion 30 projecting in the outer peripheral direction is attached and fixed to a disk drive device (not shown). The bracket 6 itself may be a base member of a disk drive. 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 using a non-magnetic material such as an aluminum alloy. The shaft 2 has a substantially cylindrical shape, and is integrally provided with a thrust plate 9 which is provided in an annularly protruding manner on the lower side of the figure. The thrust plate 9 is
It is formed substantially perpendicular to the shaft 2. The upper and lower end surfaces 25 and 40 are formed so as to be substantially parallel. Lower end surface 40 of thrust plate 9
Are positioned with respect to the bottom wall 31 of the bracket 6 so as to define the height and verticality thereof, and a herringbone-shaped dynamic pressure groove (groove) is formed on the upper end face 25 at regular intervals in the circumferential direction, although not shown. ) Is engraved. At a substantially central portion of the shaft 2, a herringbone-shaped dynamic pressure groove (groove) 19 is engraved on the outer peripheral portion 20 at a constant interval in the circumferential direction. The shaft 2 is formed using, for example, stainless steel. The shaft 2 and the bracket 6 constitute a stationary member of the brushless motor of the present invention. The rotating member (rotor) 1 rotatably supported by 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
A recording disk (not shown) is externally fitted to the outer peripheral portion 29, and the required number of recording disks received by the flange portion 28 are stacked in the upward direction in the drawing. On the inner peripheral side of the outer peripheral wall 38, the rotor magnet 4, which has been subjected to required magnetization, is disposed in a ring shape. The rotor magnet 4 has an outer peripheral wall 38.
Are positioned and fixed in the height (up and down directions in the figure) direction by the step portion 35 provided in the first position. The inner peripheral wall 37 of the hub 5 is formed in an annular shape, and is provided so as to hang downward from above in the figure. 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. Then, 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 formed of, for example, lead bronze. A cover plate 7 is fixed to the upper end of the shaft 2 over the hub 5 and the sleeve 8, thereby covering the upper portion of the hub 5. A lubricating fluid such as oil is interposed between the outer peripheral portion 20 of the shaft 2 and the inner peripheral portion 24 of the sleeve 8 which is fitted around and surrounds the shaft 2. With the relative rotation between the sleeve and the sleeve 8, a radial dynamic pressure bearing is formed. A 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 is provided. A dynamic pressure bearing is configured. 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.
Small grooves facing each other are provided on the upper end face 25 of the thrust plate 9 facing the same. This small groove is formed in an annular shape, and a gap 27 is formed in this groove. The space 27 is coated with an oil repellent for repelling the oil so that the oil does not leak outside due to surface tension. The upper end 21 of the sleeve 8
Also, a groove 22 is provided in an annular shape, and an oil repellent is applied. Similarly, oil does not leak from between the upper end 21 of the sleeve 8 and the cover plate 7. As a dynamic pressure bearing, a dynamic pressure groove for generating a dynamic pressure is engraved on the surface on the shaft 2 side. On the contrary, on the inner peripheral portion 24 side of the sleeve 8 facing the opposite side ( A dynamic pressure groove may be provided on the lower end surface 26 side (for generating thrust dynamic pressure) of the sleeve 8 (for generating radial dynamic pressure). The bottom wall 31 of the bracket 6 has a stator 3
Has been fixed. The stator 3 is a stator stack 10
And a coil 11 wound therearound. The stator stack 10 is formed by laminating a predetermined number of plates made of a thin ferromagnetic material such as an electromagnetic steel plate. 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. Among the plates constituting the stator stack 10, the upper and lower plate 1
Reference numerals 2 and 13 are bent in an L-shaped cross section in the radial direction on the rotor magnet 4 side. 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
They are arranged facing each other at a certain interval in the direction of the rotation axis (the vertical direction in the figure). That is, as is apparent from the drawing, the bent portion 15 has a slightly longer end portion than the bent portion 14. This is because the bent portion 15 located on the lower side
Is buried in the bracket 6, so that it is set longer by the buried portion. Bent portions 14 and 15 of stator stack 10
Are formed for each magnetic pole corresponding to the number of projecting magnetic poles. The configuration of these bent portions 14 and 15 substantially increases the magnetic path of the stator stack 10 to the rotor magnet 4, thereby improving the efficiency of the motor. Therefore, the stack thickness of the stator stack 10 can be reduced to reduce the thickness, 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 holes 16 are provided in an elongated shape in the circumferential direction of the bracket 6 corresponding to each magnetic pole of the stator stack 10. The distal end portion 17 of the bent portion 15 (of the lower plate 13) is inserted and buried in the hole portion 16. The buried portion is fixed by welding such as spot welding. For this reason, the front end 17 of the bent portion of the stator stack 10 and the hole 16 of the bracket 6 correspond to a predetermined position in advance, so that 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 projection 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. In the stator 3, the vibration is suppressed by being held and fixed especially on the rotor magnet 4 side where the electromagnetic vibration is high. In addition, the tip part 17 of the bent part 15 is
Since it is fixed to the bracket 6 made of a non-magnetic material, there is no adverse effect that the magnetic path is closed below the stator 3 separately from the rotor magnet 4 side. 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
Become excited and generate a current magnetic field. The hub 5 is driven to rotate 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, and the magnetic center of the rotor magnet 4 and the magnetic center of the stator 3 are defined by the rotation axis. It is slightly shifted 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. Thereby, the suction force acting on the bracket 6 from the upper side to the lower side of the drawing acts on the bracket 5, thereby preventing the hub 5 from easily coming out of the bracket 6. As described above, in the first embodiment, the stator 3
In the stator stack 10, 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 substantially opposed to the rotor magnet 4 at regular intervals in the direction of the rotation axis (vertical direction in the drawing), and the laminated thickness of the stator stack 10 is substantially increased. For this reason, the magnetic pole area of the stator 3 facing the rotor magnet 4 is increased, and 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 increased, and the thickness and size are reduced. I can do it. The bent portion 1 of the stator stack 10
5 (the distal end portion 17) also serves as a mounting foot for holding and fixing the stator 3 to the bracket 6, so that it can be easily mounted and can be stably fixed. Since this fixing is realized by welding, simpler and more reliable fixing can be performed, and the manufacturing cost can be reduced. Further, since no adhesive is used, unevenness of application and trouble of application are not required, and an accident relating to uncuring or the like does not occur. FIG. 2 is an overall sectional view showing a brushless motor according to a second embodiment. In this embodiment, the first
Only the parts and configurations that are different from those of the first 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 be a stationary member (fixed shaft type). However, 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 which rotates relative to the shaft 102 is provided on the stationary member side of the bracket 106. 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
(Inner rotor type). Further, in the second embodiment, the mounting structure of the stator 103 to the bracket 106 is different. This will be described below. In the stator stack 110, the lower plate 113 is provided with bent portions 115 and 118 on both sides of the inner and outer circumferences (left and right in the figure) in the circumferential direction. Of these, the bent portion 115 on the side facing the rotor magnet 104 serves to expand the magnetic poles and also attaches the stator stack 110 to the bracket 106 as in the first embodiment.
Make mounting feet to fix to The bent portion 118 forms another mounting foot for fixing the stator stack 110 to the bracket 106. In the first embodiment, the annular projection 18 is provided on the bracket 6, but in the second embodiment, the bent portion 118 plays the role. Therefore, also in the second embodiment, the operation and effect are the same as those of the first embodiment, and the description is omitted. The embodiment of the brushless motor according to the present invention has been described above, but the design can be changed or modified freely without departing from the gist of the present invention. Further, the combination and change of the configuration shown in the first and second embodiments can be freely selected, and other various forms and quantities shown in the present embodiment can be freely selected. The brushless motor of the present invention has the above-described structure, and has the following effects. That is, according to the brushless motor of the present invention, the bent portion is formed by bending the plate at the laminated end portion of the stator stack in a portion facing the rotor magnet so as to have an L-shaped cross section in the radial direction. For this reason, the bent portion is disposed to face the rotor magnet with a substantially constant gap, and the laminated thickness dimension of the stator stack increases by that much, so that the magnetic coupling between the rotor magnet and the stator becomes more dense. . For this reason, the efficiency is improved and the motor can be made thinner. Further, since the distal end of the bent portion of the stator stack is embedded in a stationary member such as a bracket and fixed by welding, it can be fixed securely and easily without the need for a fixing member such as an adhesive. . In addition, since the fixed portion of the stator is on the side of the rotor magnet, it is fixed at a portion where the electromagnetic vibration is the largest, so that this vibration can be reduced as much as possible. In addition, the stator
Provide a bend in the plate at the end of the stack
Then, the magnetic center of the stator and the rotor magnet
Slightly offset from the magnetic center of the
Since the magnetic force in the axial direction acts on the rolling member,
The rotation member is prevented from coming off. As described above, a brushless motor which can be reduced in size and thickness and improved in efficiency and which is easy to manufacture and has high reliability can be obtained.

BRIEF DESCRIPTION OF THE 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 sectional view showing the entire brushless motor according to a second embodiment of the present invention. [Description of Signs] 1 rotor 2 shaft 3 stator 4 rotor magnet 5 hub 6 bracket 7 cover plate 8 sleeve

Claims (1)

(57) [Claims] A stationary member; A rotating member that is supported to rotate relative to the stationary member; The required number of thin plates made of ferromagnetic material are stacked
Stator stack and wound around this stator stack
A stator coil that generates a current magnetic field when turned and excited
A stator composed of By electromagnetic interaction with the current magnetic field of the stator coil
Get rotational powerArranged on the rotating member forRotama
And a brushless motor comprisingThe rotating member is provided between the radial dynamic pressure bearing and the rotating member.
Thrust dynamic pressure acting in the direction of floating from the stationary member
Supported by a dynamic pressure bearing composed of The plate at the laminated end of the stator stack has the
L-shaped section in the radial direction at the part facing the rotor magnet
A bent part bent in a shape is provided, The tip of the bent portion is embedded in the stationary member and welded
SetAlong with The rotating member includes the stator and the rotor magnet.
The thrust dynamic pressure bearing by the magnetic force acting between
Urged in the direction opposite to the direction of action of Features
And a brushless motor.