Brakes – Internal-resistance motion retarder – Magnetic fluid or material
Reexamination Certificate
2002-03-08
2003-12-09
Butler, Douglas C. (Department: 3683)
Brakes
Internal-resistance motion retarder
Magnetic fluid or material
C188S161000
Reexamination Certificate
active
06659238
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to an electromagnetic brake and, more particularly, to an excitation type electromagnetic brake for applying brake to a rotating shaft of a motor or the like via a magnetic fluid and a non-excitation type electromagnetic brake which incorporates a permanent magnet and performs braking action via a magnetic fluid. In this specification, the motor is not limited to an electric motor, and includes a motor and the like having a rotating shaft which are driven by a fluid pressure such as an oil pressure or an air pressure.
For example, an excitation type electromagnetic brake as shown in
FIG. 8
has conventionally been used for the motor of this type.
Referring to
FIG. 8
, an excitation type electromagnetic brake
201
includes an electromagnetic brake body
203
which is mounted on a case (hereinafter referred simply to as a case)
202
a
integrated with a stator of an electric motor
202
and having a yoke member
205
with an exciting coil winding
204
, and an armature
206
serving as a brake movable member fixed to a motor rotating shaft
202
b
by a fixing member
207
via a leaf spring
208
. The armature
206
is designed so as to be capable of moving in the axial direction by an amount of deflection of the leaf spring
208
. Reference numeral
209
denotes a rectifier circuit section.
When the exciting coil winding
204
is excited, the electromagnetic brake body
203
is operated. Specifically, the armature
206
is attracted toward the yoke member
205
against the urging force of the leaf spring
208
, and comes into direct contact with the yoke member
205
or comes into contact with a friction plate, not shown, fixed to the yoke member
205
. Therefore, a braking force is created by friction, so that the rotation of the rotating shaft
202
b
is stopped.
When the exciting coil winding
204
is not excited, the armature
206
is separated from the electromagnetic brake body
203
by the urging force of the leaf spring
208
, so that the rotating shaft
202
b
is released from the brake.
However, the conventional excitation type electromagnetic brake
201
having a construction as described above has the following problems because braking action is performed by the friction:
(1) The braking force is changed by the condition of contact face of the yoke member
205
or the change in surface condition of the friction plate with passage of time, and the service life of brake is impaired by friction. Also, the condition of the friction surface changes with passage of time, so that the brake characteristics are unstable.
(2) When the armature
206
is attracted, there is produced a noise due to the contact of the armature
206
with the yoke member
205
on the electromagnetic brake body
203
side, and also there is produced a noise due to friction at the time of braking.
(3) Since there is an air gap in a magnetic path in which the electromagnetic brake body
203
produces an attracting force, it is necessary to consider the balance between the attracting force and the urging force of the leaf spring
208
.
(4) The design of magnetic circuit is very complex; for example, the adjustment of the air gap is delicate.
(5) The braking force is determined by the coefficient of friction of the above-mentioned friction, and it is very difficult to adjust the attracting force of the electromagnetic brake body
203
in the range in which attraction can be effected. Therefore, it is difficult to control the braking force.
On the other hand, for example, a non-excitation type electromagnetic brake as shown in
FIG. 9
has conventionally been used for the motor of this type.
Referring to
FIG. 9
, an electromagnetic brake
211
includes a brake disc
212
serving as a brake movable member, which is fixed to an output rotating shaft
214
of a motor
213
, an electromagnetic brake body
215
having a yoke member
217
on the stator side with a coil winding
216
, an armature
218
integrated with a brake lining material
218
a
, and a spring
219
which urges the armature
218
in the direction in which the armature
218
is separated from the electromagnetic brake body
215
to operate the brake. (The brake lining material
218
a
is sometimes integrated with the brake disc
212
.)
When the coil winding
216
is not energized, the armature
218
is separated from the electromagnetic brake body
215
by the urging force of the spring
219
, and the brake lining material
218
a
affixed to the armature
218
is brought into contact with the brake disc
212
. Thereby, a braking force is produced by friction, and thus brake is applied to the output rotating shaft
214
of the motor
213
.
Also, when the coil winding
216
is energized, the armature
218
is attracted to the electromagnetic brake body
215
against the urging force of the spring
219
, and the brake lining material
218
a
is separated from the brake disc
212
, by which the rotating shaft
214
is released from the brake.
In this electromagnetic brake
211
, two or more pins
220
are erectly provided on the yoke member
217
, and the pins
220
are engaged with pin holes
218
b
formed in the armature
218
, by which the armature
218
is prevented from rotating together with the brake disc
212
, and is guided slidably in the direction of the rotating shaft.
However, the conventional non-excitation type electromagnetic brake
211
constructed as described above has problems in that the brake force is changed by the change in surface condition of the brake lining material
218
a
with passage of time, and the service life of brake is impaired by the friction of the brake lining material
218
a
, and that there is produced a noise due to friction at the time of braking, and also when the armature
218
is attracted due to excitation, there is produced a noise due to the contact of the armature
218
with the yoke member
217
on the electromagnetic brake body
215
side.
Furthermore, since the armature
218
has a backlash in the direction of rotation, the rotating shaft
214
has a play when being held by the electromagnetic brake
211
.
In particular, the electromagnetic brake
211
has problems in that there is a degree of (a non-negligible degree of) air gap in a magnetic path in which the electromagnetic brake body
211
produces an attracting force at the time of excitation, so that it is necessary to consider the balance between the attracting force and the urging force of the spring
219
, and that the design of magnetic circuit is very complex; for example, the adjustment of the air gap is delicate.
OBJECT AND SUMMARY OF THE INVENTION
The present invention has been made in view of the above situation, and accordingly an object thereof is to provide an excitation type electromagnetic brake and a non-excitation type electromagnetic brake in which the above problems are solved, wear of the braking portion is eliminated, whereby the service life thereof can be prolonged, and also a noise produced by the braking portion can be eliminated.
Another object of the present invention is to provide an excitation type electromagnetic brake and a non-excitation type electromagnetic brake in which regarding the construction, in brake application, a movable portion is eliminated, so that the construction can be made simple, and also the number of parts can be decreased.
To achieve the above objects, the present invention provides an electromagnetic brake comprising an electromagnetic brake body having a yoke member with a coil winding and a brake movable member formed of a magnetic material, which is disposed via an air gap in a magnetic path formed by the electromagnetic brake body and is fixed to a rotating shaft, wherein a magnetic fluid is interposed or filled in the air gap, and fluid leakage preventive means is formed or disposed between the electromagnetic brake body and the brake movable member to prevent the magnetic fluid from leaking to the outside, whereby the rotating shaft is braked using the electromagnetic brake when the coil winding
Nakano Masami
Saito Makoto
Butler Douglas C.
Oriental Motor Co., Ltd.
Trop Pruner & Hu P.C.
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