Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2001-02-13
2002-09-10
Tamai, Karl (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S216055, C310S256000
Reexamination Certificate
active
06448682
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a laminated motor core, a method of manufacturing such a laminated core, a motor incorporated with such a laminated core, and an ink-jet recording apparatus provided with such a motor, and particularly relates to restraint of vibrations of a laminated core used in a stepping motor, a servo motor, or the like.
BACKGROUND ART
Conventionally, a laminated core to be used as a stator core of a stepping motor or the like is formed in such a structure that a plurality of core pieces
10
of magnetic material are laminated, similarly to that which is shown in
FIGS. 1 and 2
. Each core piece
10
is formed with such a flat shape as illustrated, by progressive forming by a press, in advance. Thereafter, one core piece
10
is put on the top of another core piece
10
, and half blanking is performed in caulking portions
14
as illustrated so that the two core pieces
10
are fitted and fixed to each other. Such a process is repeated to fix a large number of core pieces
10
to each other sequentially to thereby form a laminated core
1
.
The laminated core
1
is provided with an outer frame portion
11
formed in the outer circumferential portion, and teeth portions
18
formed in the inner circumferential portion. The teeth portions
18
are constituted by, for example, eight bridge portions
12
projecting inward from the inner circumferential surface of the outer frame portion
11
, and magnetic pole portions
13
formed on the forward ends of these bridge portions
12
, respectively. A surface-roughed shape constituted by mountain portions
13
a
and groove portions
13
b
formed alternately in the direction of rotation of a not-shown rotor is formed in the inner circumferential edge portion of each of the magnetic pole portions
13
. The area surrounded by these eight magnetic pole portions
13
forms an inner hole
16
which is substantially circular, so that a not-shown rotor is received in this inner hole
16
.
However, in a motor in which such a laminated core as mentioned above is used as a stator core, large noise may be caused when the motor is driven. Though this noise is considered to be caused for various reasons, the present inventors have found, through various analyses, that the main reason is in that the core pieces
10
of the stator core vibrate in the vicinities of the magnetic pole portions
13
, and the core pieces
10
resonate in the case where a certain condition is satisfied.
In order to restrain such vibrations or resonance, it is considered necessary to fix the core pieces
10
to each other at a portion each of the teeth portions
18
.
Therefore, caulking portions
15
was provided in the bridge portions
12
of the respective teeth portions by way of experiment. As a result, it was found that the above-mentioned vibrations or resonance could be reduced effectively. However, in this case, the number of the caulking portions
15
increased correspondingly to the number of the teeth portions
18
, so that not only it was necessary to make mold adjustment which requires high technique and skill, but also the durability of the mold was required unreasonably. Accordingly, the manufacturing cost was increased.
Further, caulking portions were provided in the magnetic pole portions
13
of the teeth portions
18
by way of experiment. In this case, not only it was difficult to perform half blanking but also it was difficult to ensure the strength of the mold because the plane shapes of the respective core pieces
10
are formed to be narrow in the magnetic pole portions
13
. Accordingly, manufacturing was difficult in practical use.
Furthermore, another method in which the core pieces
10
are bonded with each other by a bonding agent or tape with a bonding agent may be considered. However, not only it is comparatively difficult to automate this bonding process and it requires high cost to provide equipment therefor, but also there is such a danger that the bonding agent is eluted in the process of cleansing the stator core to make the core pieces
10
separate from each other.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide a laminated motor core in which vibrations of core pieces causing motor noise can be restrained at a low cost, and a method of manufacturing such a laminated core.
It is another object of the present invention to provide a motor and an ink-jet recording apparatus, in which noise is prevented from being made.
(1) According to an aspect of the present invention, provided is a laminated core of a motor in which a plurality of magnetic plates are laminated one on another, the laminated core being provided with magnetic poles each having a roughed surface constituted by mountain portions and groove portions formed alternately in the direction of rotation of the motor, characterized in that welded portions for firmly fixing the magnetic plates to each other are provided in surfaces of the groove portions formed in the magnetic poles. According to this invention, the welded portions for firmly fixing the magnetic plates to each other are provided in the surfaces of the groove portions of the magnetic poles, so that it is possible to firmly fix the magnetic plates to each other in the magnetic poles to which a magnetic force is applied. Accordingly, it is possible to restrain the generation of vibrations, so that it is possible to reduce motor noise. In addition, the welded portions are formed in the groove portions where the magnetic flux density is small, so that it is possible to restrain deterioration of the magnetic characteristic caused by heat at the time of welding.
(2) According to another aspect of the present invention, in the laminated core of a motor described above in the item (1), the welded portion is provided in the surface of the groove portion formed in the vicinities of the central portion of each of the magnetic poles in the direction of rotation. As is understood from magnetic flux density distribution and magnetic flux distribution in
FIGS. 4 and 5
which will be described later, the magnetic flux density becomes lowest, for example, to be in a range of from 2,500 to 5,000 gausses in the groove portions near the central portions of the magnetic poles. Since the welded portions are formed in such positions (near the central portions of the magnetic pole portions in the direction of rotation), it is possible to further reduce the deterioration of the magnetic characteristic, and it is also possible to obtain symmetry of a fixation force in the magnetic pole portions to thereby make it possible to restrain the generation of vibrations efficiently.
(3) According to a further aspect of the present invention, in the laminated core of a motor described in the above item (1), the welded portions are provided in the surfaces of the groove portions respectively formed on opposite end sides of each of the magnetic poles in the direction of rotation. On the opposite end dies of each magnetic pole, vibrations with large amplitude are apt to be produced because the opposite end sides are in the most distant positions from the base of the bridge portion. Since the welded portions are provided in such portions, it is possible to restrain vibrations effectively.
(4) According to another aspect of the present invention, provided is a laminated core of a motor in which a plurality of magnetic plates are laminated one on another, the laminated core being provided with magnetic poles each having a roughed surface constituted by mountain portions and groove portions formed alternately in the direction of rotation of the motor, characterized in that welded portions for firmly fixing the magnetic plates to each other are provided on both back-surface-side shoulder portions of each of the magnetic poles. The magnetic flux density is a comparatively small in the back-surface-side shoulder portions of the magnetic poles. Accordingly, deterioration of the magnetic characteristics caused by heat at the time of welding is too small to give a bad influence to the characteris
Sakagami Eimatsu
Umetsu Kazushige
Dinh Le Dang
Ladas & Parry
Seiko Epson Corporation
Tamai Karl
LandOfFree
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