Electrical generator or motor structure – Dynamoelectric – Linear
Reexamination Certificate
2001-06-22
2003-06-03
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Linear
Reexamination Certificate
active
06573623
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to sliding means that have been extensively used in machines and instruments as diverse as semiconductor manufacturing apparatus, machine tools, industrial robots, conveyors and others. It is more particularly concerned with a sliding means with built-in moving-magnet linear motor, in which an armature winding is arranged in a stationary bed while a field magnet is installed in a moving table.
2. Description of the Prior Art
In recent years, multi-axis stages and moving mechanisms employed in the diverse technical fields as described above have required more and more sliding means, which are 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 sliding means involve two broad types. The first, called moving-coil linear motor, has a stator of field magnet mounted on a stationary bed, and moving-armature windings arranged on a table movable lengthwise of the bed in sequence one after another such that they lie a preselected phase angle. The second, called moving-magnet linear motor, has a stator of armature windings arranged lengthwise over the entire length of a bed, and a moving-field magnet of permanent magnet arranged on a table movable in a sliding manner along the length of the bed.
Japanese Patent Laid-Open No. 322232/1996 discloses a linear motor installed in a knitting machine to drive a knitting needle in reciprocating motion. The liner motor is comprised of a plurality of built-in moving-coil liner motor units each of which has a moving assembly composed of a backing plate made therein a window, a resilient sheet member fixed on any one side of the backing plate with adhesive, and exciting windings, for example three windings, arranged on any one surface of the sheet member in a manner to be partly accommodated in the window. The exciting winding is made in the form of flat ellipse where the axial direction of the winding extends thickness-wise of the linear motor unit. The moving assembly is arranged for linear movement between stator assemblies confronting one another, each of which is composed of a backing plate made of ferromagnetic material such as steel, and a plurality of permanent magnet, for example six pieces arranged on the backing plate in juxtaposition along the traveling direction of the moving assembly. The construction in which the exciting windings are accommodated in the associated window in the backing plate reduces the overall thickness or height of the moving assembly. Linear displacement-measuring means is composed of a linear scale extending along the moving direction of the moving assembly, and a sensor head installed on any one of the confronting stator assemblies.
A dc linear motor is disclosed in Japanese Patent Laid-Open No. 47239/1996, in which any one of forward and aft end poles in the field magnet is made insensitive to a pole discriminating element. With the do linear motor recited just above, a moving table is provided on the underside thereof with a magnet yoke, underneath which a field magnet is arranged in opposition to primary armature windings mounted on a stationary bed. The field magnet is made in the form of rectangle in which unlike poles or N-, S-poles are arranged alternately along the fore-and-aft direction thereof. Any one of the forward and aft end poles is made insensitive at a surface opposing to a Hall-effect element to discern the end of the field magnet for monitoring a position of the moving table. This makes it possible to reduce a deviation in number of the coil sides of the armature windings, which might contribute to really generating propulsion, thus realizing the steady propulsion.
A moving-magnet brushless dc linear motor is disclosed in Japanese Patent Laid-Open No. 298946/1989, in which a semiconductor rectifier is arranged for each coil, and two sets of three-phase coil groups are arranged to provide a linear motor of three-phase conduction system.
A sliding means adapted to be used for machine tools and industrial robots is disclosed in Japanese Patent Laid-Open No. 266659/1997, which is a senior copending application of the present applicant. The prior sliding means includes a driving source made of an electromagnetic linear actuator and a built-in moving-magnet uniaxial linear motor to control with precision a position of a driven article. With the prior sliding means cited just above, an electromagnetic linear actuator is arranged between a moving table and stationary bed of steel or magnetic material and at least any one of the table and the bed is constructed to serve a part of magnetic circuit of the electromagnetic linear actuator, concretely the function of either magnet yoke or coil yoke. The prior sliding means has no need of providing separately yokes for establishing magnetic circuit, which might make the sliding means bulky, thus reduced in the number of parts required, and made inexpensive in production cost and slim in construction.
The sliding means disclosed in the above Japanese Patent Laid-Open No. 266659/1997 will be explained below, with referring to
FIGS. 18 and 19
. A sliding means
51
with an built-in linear motor is composed of a stationary bed
52
and the moving table
53
, both of which are made of magnetic material such as steel to serve the function of magnetic circuit, or magnet yoke and coil yoke, thereby rendering the linear motor small or compact in size. The sliding means
51
with built-in linear motor has the stationary elongated bed
52
, and the moving table
53
mounted on the bed
52
for linearly reciprocating movement lengthwise of the bed
52
by virtue of linear motion guide units
54
. The linear motion guide units
54
are comprised of two track rails
55
arranged on the bed
52
in parallel with each other, and four sliders
56
fitting over the associated track rail
55
for sliding movement. In the linear motion guide units
54
, load raceway areas are provided between confronting raceway grooves, one of which is formed on lengthwise sides of the track rails
55
while the counterpart is formed on the sliders
56
. The sliders
56
are allowed to move with smooth along the track rails
55
as rolling elements run through the load raceway areas. The table
53
is bored with holes
58
through which screws fit to fix a work on the table
53
.
An end block
61
and a connector block
62
are secured to the lengthwise opposing ends of the bed
52
, each to each end, with fixing bolts
63
,
64
to define a tolerable range of operating stroke of the table
53
. The bed
52
is made with holes
65
through which bolts
66
fit to anchor the bed
52
to a platform.
An armature
70
, which is a primary side of the sliding means
51
, is comprised of a coil board
71
and eight pieces of armature windings
72
arranged on the underside of the coil board
71
in juxtaposition along the moving direction of the table
53
. The bed
52
is recessed lengthwise at
73
on the upper surface thereof, where the armature
70
is accommodated through an insulating film
74
. Hall-effect elements
75
are arranged on the coil board
71
in conjunction with the armature windings
72
, each to each winding. The Hall-effect elements
75
are to issue a signal in response to an amount of magnetic flux created by a secondary field magnet
90
, which is detected when the field magnet
90
approaches the Hall-effect elements
75
. Excitation of the armature windings
72
is controlled depending on the signal issued out of the Hall-effect elements
75
. The armature
70
is jointed to the bed
52
by means of machine screws
76
fitting through spacers
77
, which make abutment at their opposing ends against both the bed
52
and the coil board
71
at locations offset widthwise of the bed
52
between any two adjacent armature windings
72
from one another.
The bed
52
is also made
Fujisawa Shoji
Ohno Masaki
Tsuboi Takaaki
Browdy and Neimark , P.L.L.C.
Jones Judson H.
Nippon Thompson Co. Ltd.
Ramirez Nestor
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