Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2001-10-23
2004-03-02
Le, Dang (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S06700R, C360S099080
Reexamination Certificate
active
06700256
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a brushless motor, and in particular to a connection construction between a rotor frame, a turntable, a hub, a rotor boss, and the like, and a shaft of a brushless motor rotationally driven primarily with an information-recordable/reproducible disk such as a compact disk, a video disk, or a magnetic disk being mounted on the turntable, hub, or the like. Alternatively, the present invention relates to a connection construction between a rotor frame, a turntable, a hub, a rotor boss, and the like, and a shaft of a brushless motor rotationally driven with a load such as a rotational polygon mirror mounted thereon.
2. Description of the Prior Art
A conventional brushless motor is disclosed in, for example, Japanese Patent Unexamined Laid-Open Publication 8-289523 (published in 1996).
FIG. 8
shows a construction of the conventional brushless motor. FIG.
8
. is a cross-sectional view of an embodiment of the conventional brushless motor. In
FIG. 8
, numeral
71
denotes a shaft for transmitting rotation. Numeral
72
denotes a rotor frame in which a ringular magnet
73
circumferentially multipolar-magnetized is fixed by performing either press-fitting or adhesion. A projected annular portion
74
is formed in a central portion of the rotor frame
72
, and the shaft
71
is directly press-fitted thereinto. In this manner, a rotor assembly
75
is configured.
Numeral
76
denotes a bracket, in which a burring process is applied on a central portion of a steel plate so that a bearing housing is formed and a mounting-base function is integrated. A bearing
77
for rotationally supporting the shaft
71
is press-fixed inside a burring portion of the bracket
76
. A stator core
78
, which is wound with a stator coil
79
around an iron core via resin insulation, is press-fixed in an outer portion of the burring portion of the bracket
76
. At least a part of a circuit for driving and controlling the motor is mounted on a printed circuit board
80
, and the printed circuit board
80
is adhered and fixed via a double-side adhesive tape onto a planar portion of the bracket
76
. An end of the stator coil
79
is wired on the printed circuit board
80
. In this way, a stator assembly is constructed.
Numeral
81
denotes a disengagement-preventing piece for preventing thrust-directional disengagement of the rotational assembly, i.e., the rotor assembly
75
, where the disengagement-preventing piece
81
is formed through metal-press processing and is press-fitted onto one end of the shaft
71
. Numeral
82
denotes a bottom plate holding a thrust-directional load of the rotor assembly
75
and the bottom plate
82
is press-fitted and fixed at a burring-portion entrance of the bracket
76
via a thrust plate
83
formed of an abrasion-resistant resin.
As described above, the shaft
71
is directly press-fitted in the projected annular portion
74
positioned in the central portion of the rotor frame
72
. Thus, the connection between the shaft and the frame is simplified and secured.
However, there are tendencies in which the overall size and the thickness are reduced for brushless motors that are used for information-recording and reproducing devices, such as compact disks, video disks, or magnetic disks, or brushless motors that are used for devices rotationally driven with a load such as a rotational polygon mirror being mounted. To meet requirements in the tendencies, however, when a projected annular portion of a rotor frame and a rotor boss that are connected to a shaft are reduced in length, the difficulty increases in maintaining the strengths of the connected portions.
In addition, in a technique for directly press-fitting, for example, the projected annular portion of the rotor frame onto the shaft, the precision of the rotor assembly depends on the precision of each component with the projected annular portion of the rotor frame. However, in the tendency requiring a higher-speed operation of an information-recording/reproducing device, such as a compact disk, a video disk, or a magnetic disk, the strictness of precision is increasing year by year in precision regarding deflective rotation of a rotational unit for a turntable and a rotor frame of a brushless motor. The strictness of the aforementioned precision is also increasing for a rotational unit such as a rotor boss of a brushless motor used for mounting, for example, a rotational polygon mirror. The conventional connections between a shaft and a rotor frame and between a shaft and a rotor boss therefore encounter difficulties in satisfying the requirements for high precision regarding the deflection.
Furthermore, it is increasingly necessary to obtain a high precision of circumferential portions of the projected annular portion of the rotor frame and the outer diameter portion of the rotor boss. The aforementioned precision is important to perform high-precision mounting of a clamping mechanism that is used for self-clamping an information-recording/reproducing disk such as a compact disk, a video disk, or a magnetic disk, or a rotational polygon mirror that is to be mounted onto the rotor boss.
However, problems are caused in performing accurate positioning and mounting operation because of variations in the outer diameters according to plastic deformation. The plastic deformation occurs on the circumferential portions of the projected annular portion of the rotor frame, the outer diameter of the rotor boss, or the like when the shaft is press-fitted.
In addition to the above-described conventional example, Japanese Utility Model Unexamined Laid-Open Publication No. 63-29369 (published in 1988) discloses another example a configuration of which is shown in
FIGS. 9A
,
9
B,
9
C, and
9
D.
In this example, the configuration includes an annular groove
91
and a groove
93
, as shown in
FIGS. 9A
,
9
B,
9
C, and
9
D. The annular groove
91
is circumferentially formed on a rotational shaft
90
. The groove
93
in the rotational-shaft direction is formed on a bore cylindrical wall of a rotational unit
92
provided adjacent to the annular groove
91
. An adhesive
94
is filled into a gap between the annular groove
91
and the groove
93
formed in the direction of the rotational shaft, and the adhesive is then cured. In this way, the configuration is arranged such that the rotational shaft
90
and the rotational unit
92
are connected together to integrally rotate. By this arrangement, the configuration enables the implementation of a rotational unit that allows long-term stable quality to be maintained without an increased number of components, that facilitates assembly, and that produces reduced vibrations.
However, the above configuration requires the process of forming the annular groove. Furthermore, the configuration requires the annular groove to be formed in the rotational-shaft direction on the bore cylindrical wall. The configuration thus requires the complicated grooves to be formed. This creates a problem in that the configuration is not economically advantageous.
When the shaft and the rotor frame are connected by using the adhesive, the centers thereof may deviate from each other because of the gap for adhesion. This deviation causes radial deflections on a clamping mechanism that is used for self-clamping an information-recording/reproducing disk (such as a compact disk, a video disk, or a magnetic disk), a rotor boss that is used for mounting a rotational polygon mirror, or the like. For this reason, a problem occurs in that a load member, such as a compact disk, a video disk, a magnetic disk, or a rotational polygon mirror, causes decentering with respect to the rotational center. During high-speed rotation of the rotor assembly, the decentering causes unbalanced rotation, and the unbalanced rotation causes great vibrations.
Another example is disclosed in Japanese Patent Unexamined Laid-Open Publication No. 8-192285 (published in 1996). In this case, the configuration is arranged such that a rotation
Fukutani Hideshi
Ikeno Hiroshi
Takata Norimasa
Le Dang
Matsushita Electric - Industrial Co., Ltd.
Wenderoth , Lind & Ponack, L.L.P.
LandOfFree
Brushless motor and production method therefor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Brushless motor and production method therefor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Brushless motor and production method therefor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3200860