Electrical generator or motor structure – Dynamoelectric – Linear
Reexamination Certificate
2001-08-20
2004-05-11
Mullins, Burton S. (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Linear
Reexamination Certificate
active
06734583
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a slider unit with a built-in moving-coil linear motor, which has been extensively used in semiconductor and liquid crystal display industries, measuring instruments, assembling machines, machine tools, industrial robots, conveyors and others. More particular, the present invention relates to a slider unit with a built-in moving-coil linear motor of the type in which an exciting coil is installed in the side of moving element.
2. Description of the Prior Art
In recent years, multi-axis stages and moving mechanisms such as X-Y plotters employed in the diverse technical fields as stated just above have required more and more a slider unit, which is compact or slim in construction and light in weight, and moreover able to operate with high propulsion, high speed and high response to provide high speed travel and accurate position control for works, tools, articles and instruments. Linear motors commonly used in the slider units involve two broad types. The first, called moving-magnet linear motor has a stator of an armature coil arranged lengthwise over the entire length of a bed of stationary part, and a moving-field magnet of permanent magnet arranged on a table movable in a sliding manner along the length of the bed. The second, called moving-coil linear motor has a stator of field magnet mounted on the bed, and moving-armature coils distributed in space one after another on the table such that they are a preselected electrical angle out of phase.
A moving-coil linear motor is disclosed in Japanese Patent Publication No. 49099/1983. As shown in FIGS. 1 and 2 in the Japanese publication recited earlier, the prior linear motor has flat permanent-magnet pieces that are each magnetized in thickness-wise direction. The permanent magnets are arranged such that the poles on either magnet alternate lengthwise in polarity along a traveling direction of a moving element while like poles are placed in opposition to each other across the traveling direction of the moving element. A center yoke is arranged between confronting like poles in such a relation as to oppose the permanent-magnet pieces. The moving coil is composed of two winding parts each of which has a length half the width of the permanent-magnet piece, the two winding parts being arranged on a coil bobbin fit in the center yoke. Thus, the moving coil is allowed to move in a clearance defined between the permanent magnets and the center yoke.
Another example of the prior moving-coil linear d-c motor is disclosed in Japanese Patent Laid-Open No. 254682/1987. The prior moving-coil linear d-c motor, as seen from FIGS. 1 and 2 in the publication cited above, is the same found in Japanese Patent Publication No. 49099/1983, other than the moving part of coils composed of more than one set of three-phase coil.
Japanese Patent Laid-Open No. 107728/1995 discloses a linear d-c motor to drive an X-Y table, in which the stationary side is composed of a yoke of roughly U-shaped configuration in cross section and a permanent magnet secured on a bottom of the yoke, while a moving side is supported on the stationary side for lengthwise reciprocation and composed of an iron core encircled with coils, and a pair of magnetic members attached to fore-and aft ends of the iron core.
Referring now to
FIGS. 11 and 12
, there is shown a prior slide unit with a built-in moving-coil linear motor disclosed in Japanese Patent Laid-Open No. 333435/2000, which is co-pending senior application. In the accompanying drawings,
FIG. 11
is a perspective view showing the slide unit having a built-in moving-coil linear motor, while
FIG. 12
is an illustration to explain how the linear motor operates to drive the slider unit.
A slider unit
70
is of an elongated structure made reduced in the overall height and mainly comprised of a bed
2
for a base member mounted to any one, ordinarily stationary side, not shown, of relatively movable parts by means of screws fit in fixing holes
4
, and a table
10
on which is mounted a counterpart, ordinarily a work, not shown, of the relatively movable parts. The bed
2
has a shallow U-shape, when viewed in cross section traversing the moving direction of the table
10
, which is composed of an elongated bottom
2
b
and upright walls
2
a
arranged at widthwise opposing edges of the bottom
2
b
. A pair of track rails
3
is arranged lengthwise of the bed
2
in parallel with each other at a height identical with each other and fixed to the bed
2
with machine screws
17
. The table
10
is secured by machine screws
46
onto more than one sliding element
11
that rides on the elongated track rails
3
for sliding movement. A moving-coil linear motor
20
inboard the slider unit
70
is comprised of a magnet yoke
21
having an U-shaped configuration in cross section, a pair of field magnets
30
,
31
attached to the magnet yoke
21
, and a moving-coil assembly
40
supported on the table
10
.
Attached on lengthwise opposing ends of the bed
2
are end blocks
5
, one to each end, to define a tolerable stroke range where the table
10
is allowed to move along the track rails
3
. Recesses
7
opened downwards are formed at the outermost end faces
5
a
of the end blocks
5
. An operator may easily lift or carry the slider unit
70
by putting his hands on the recesses
7
. Stoppers
8
of elastic body such as urethane rubber are attached to inside surfaces
5
b
of the end blocks
5
, one to each end block, to provide buffers for protecting the table
10
from a collision against the end blocks
5
when the sliding element
11
comes close to the limit of its stroke. Limiters, although not shown, are arranged on the lengthwise opposing ends of the bed
2
and fixed to the bed
2
with machine screws
19
, while the table
10
has detecting means to sense the limiters when approaching any one of the opposing ends of the bed
2
.
The table
10
, while secured by machine screws
46
onto more than one sliding element
11
, is made with many threaded holes
12
, four holes shown in figures, for fixing a work. The sliding element
11
constitutes, in combination with the track rails
3
, for example a small linear motion guide unit
16
in which rolling elements are allowed to run through recirculating passage including raceways defined between the confronting surfaces of the rack rails
3
and the sliding elements
11
, and turnarounds and return passages in the sliding elements
11
.
The table
10
is allowed to move lengthwise of the bed
2
with respect to the bed
2
by virtue of the small linear motion guide units
16
. Both the bed
2
and the table are made of aluminum alloys to reduce in weight the slider unit
70
, improving the acceleration performance, and realizing high speed and high responsibility.
A linear motor
20
drives the table
10
along the bed
2
. The moving-coil assembly
40
is supplied with electric power through a power line. Signals representing the positions of the table
10
with respect to the bed
2
are applied to an external controller where the electric power supplied through the power line is regulated, depending on information as to the positions applied via the sensor cord.
The moving-coil linear motor
20
inboard the slider unit
70
includes a magnet yoke
21
of U-shape in cross section perpendicular to the moving direction of the table
10
to support the field magnets
30
,
31
thereon. The magnet yoke
21
will be considered a stator part of the moving-coil linear motor
20
, which extends lengthwise over the entire length of the bed
2
and is mounted to the bed
2
. The magnet yoke
21
is composed of an upper web
22
and a lower web
23
, which are arranged in opposing relation to each other to provide an elongated gap
32
between them, and a connecting web
24
interconnecting integrally the confronting upper and lower webs
22
,
23
at any one side of widthwise opposing edges. The magnet yoke
21
, although made thin in thickness and slim in construction, may be kept high in it
Fujisawa Shoji
Togashi Tsutomu
Browdy and Neimark , P.L.L.C.
Jones Judson H.
Mullins Burton S.
Nippon Thompson Co. Ltd.
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