U.S. patent number 3,805,203 [Application Number 05/327,958] was granted by the patent office on 1974-04-16 for electromagnetic thrusters.
This patent grant is currently assigned to General Motors Corporation. Invention is credited to John I. Deckard.
United States Patent |
3,805,203 |
Deckard |
April 16, 1974 |
ELECTROMAGNETIC THRUSTERS
Abstract
Solenoid devices intended primarily to exert a force closely
proportional to energizing current and particularly adapted for use
in fluid pressure and flow controlling systems. The device includes
an annular housing of magnetic material enclosing a nonmagnetic
bobbin on which a coil is wound. An armature reciprocable within
the bobbin in proximity to a pole piece of the housing exerts a
force on a plunger extending through the pole piece. The controlled
fluid may communicate with the interior of the bobbin; one end of
the bobbin is closed and the other end is sealed to the housing so
that the fluid may not escape from the device.
Inventors: |
Deckard; John I. (Grand Rapids,
MI) |
Assignee: |
General Motors Corporation
(Detroit, MI)
|
Family
ID: |
23278846 |
Appl.
No.: |
05/327,958 |
Filed: |
January 30, 1973 |
Current U.S.
Class: |
335/239;
251/129.14; 335/260; 335/258 |
Current CPC
Class: |
H01F
13/00 (20130101) |
Current International
Class: |
H01F
13/00 (20060101); H01f 007/18 () |
Field of
Search: |
;335/239,240,258,260,262
;251/129 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Harris; George
Attorney, Agent or Firm: Fitzpatrick; Paul
Claims
1. An electromagnetic force-exerting device comprising, in
combination, a housing; a pole piece abutting the housing including
a hollow boss extending into the housing; an annular bobbin in the
housing piloted at one end of the bobbin on the said boss, the
bobbin including a portion providing a pilot connection between the
other end of the bobbin and the housing and locating with the boss
the axis of the bobbin; a solenoid on the bobbin; an armature
reciprocable within the bobbin, the armature and boss having
confronting portions defining an air gap; an actuating rod slidable
within the said boss actuatable by the armature; means closing the
said other end of the bobbin against escape of fluid; and means
providing a fluid seal between the bobbin and the pole piece; the
actuating rod and armature having sufficient clearance from the
pole piece and bobbin for flow of fluid upon reciprocation thereof;
the housing, pole piece, and armature being of a magnetic material
and the bobbin and
2. An electromagnetic force-exerting device comprising, in
combination, a generally cylindrical housing; a pole piece abutting
the housing at one end including a hollow boss extending into the
housing; an annular bobbin in the housing including a cylindrical
portion piloted at one end of the bobbin on the said boss, the
cylindrical portion providing a pilot connection between the other
end of the bobbin and the housing and locating with the boss the
axis of the bobbin; a solenoid on the bobbin; an armature
reciprocable within the cylindrical portion of the bobbin, the
armature and boss having confronting portions defining a radial air
gap; an actuating rod slidable within the said boss actuatable by
the armature; means closing the said other end of the cylindrical
portion against escape of fluid; and means providing a fluid seal
between the cylindrical portion and the pole piece; the actuating
rod and armature having sufficient clearance from the pole piece
and bobbin for flow of fluid upon reciprocation thereof; the
housing, pole piece, and armature being of a
3. An electromagnetic force-exerting device comprising, in
combination, a generally cylindrical housing; a pole piece abutting
the housing at one end including a hollow boss extending into the
housing; an annular bobbin in the housing piloted at one end of the
bobbin on the said boss, the bobbin including a portion extending
into an opening in the housing providing a pilot connection between
the other end of the bobbin and the housing and locating with the
boss the axis of the bobbin; a solenoid on the bobbin; an armature
reciprocable within the bobbin and spaced radially from the housing
by the bobbin, the armature and boss having confronting portions
defining an air gap; an actuating rod slidable within the said boss
actuatable by the armature; means forming part of the bobbin
closing the said other end of the bobbin against escape of fluid;
and means providing a fluid seal between the bobbin and the pole
piece; the actuating rod and armature having sufficient clearance
from the pole piece and bobbin for flow of fluid upon reciprocation
thereof; the housing, pole piece, and armature being of a magnetic
material and the bobbin and actuating rod being nonmagnetic.
Description
My invention is directed to electromagnetic thrusters; that is, to
devices which are intended to exert a force which is a function,
preferably a linear function, of the energization of a coil or
solenoid which is a part of the device. The thrusters according to
my invention are particularly adapted for use in engine controlling
systems and in general in systems in which the force exerted may be
a means for providing an interface between an electrical control
system and a fluid flow or pressure regulating system. The solenoid
devices according to my invention are of structure which is
particularly adapted to leakproof operation, to linearity of
response, and to economical fabrication and compact dimensions.
Generally speaking, in its preferred embodiment, the thruster
comprises a cup-shaped housing, having an annular pole piece
closing one end of the housing, and having a bobbin mounted within
the housing defining a guide for an armature reciprocable within
the bobbin. The armature is attracted to the pole piece upon
energization of a solenoid wound around the bobbin. The fluid may
be displaced past the armature in case of its movement, and the
bobbin is sealed to the pole piece to contain fluid within the
enclosure defined by the bobbin. Force is transmitted from the
armature by a push rod or plunger extending through the pole
piece.
The nature of my invention and its advantages will be more fully
apparent from the succeeding detailed description of preferred
embodiments of the invention and the accompanying drawings.
FIG. 1 is a longitudinal sectional view of an electromagnetic
device embodying the invention.
FIG. 2 is a similar view of a modified device.
FIG. 3 is a fragmentary view of the application of the device of
FIG. 2 to valve operation.
FIG. 4 is a graph illustrating the force characteristics of the
device as a function of current.
Referring first to FIG. 1, the electromagnetic force exerting
device comprises a cup-shaped housing 2 defining a generally
cylindrical internal chamber 3 recessed as indicated at 4 at the
open end of the housing. An annular pole piece 6 fitted in the
recess 4 substantially closes the open end of the housing. The pole
piece includes an external boss 7 and an internal boss or pole 8
extending into the housing along its axis. The housing and pole
piece are made of a suitable magnetic material such as soft silicon
core iron such as is used for transformer cores. The solenoid or
coil 10 which generates the magnetic force is wound on a bobbin or
spool 11 made of a suitable nonmagnetic material. The preferred
material is a glass fiber reinforced acetal resin derived by
polymerization of formaldehyde sold by du Pont under the trademark
Delrin 570. The bobbin includes a flange 12 which abuts the inner
surface of the pole piece 6 and is impinged between it and a
shoulder 14 at the bottom of recess 4. It includes a central hollow
cylindrical portion 15 and a second flange 16.
The cylindrical portion defines internally a guideway for a
magnetic reciprocable armature 18, also of soft iron. The end of
the bobbin remote from pole piece 6 extends into and is located
radially by a bore 19 in the closed end of the housing. This end of
the bobbin is closed by an integral wall 20. The portion of the
bobbin adjacent the pole piece 6 fits over the pole 8 so that the
bobbin is located radially by its piloted fit over this pole and
with the interior of bore 19 and is located axially between the
pole piece 6 and the housing 2.
The armature 18 is approximately of cylindrical shape with a
conical forward end 22 which is disposed adjacent to a
corresponding conical recess 23 in the pole, the device defining an
air gap between the surfaces 22 and 23. There is also an air gap
between the armature and the housing at the bore 19. Armature 18 is
tapped to receive the threaded end 24 of an actuating rod 26, the
latter being reciprocable in a suitable bore 27 along the axis of
the pole piece. Preferably, the armature has two shallow flanges 28
and 29 which bear against the interior of the bobbin cylinder 15.
These flanges are partially cut away as indicated at 31 and 32 to
permit fluid to flow freely past the armature when it moves.
Assuming that the actuating rod 26 is exposed to fluid, the fluid
may enter the device through the bore 27 and fill the space around
the armature. It is prevented from leaking by an O-ring 34 disposed
between the forward face of the bobbin and the pole piece. It is
essential to fast transient response that no significant fluid
pressure differential is generated by shifts of the armature. If
slow response is acceptable, some fluid damping of armature
movement by fluid in the cylinder 15 may be desirable.
The boss 7 of the pole piece may be mounted in a suitable recess in
a device which is to be controlled and the actuator may be held in
place by suitable clamping means engaging a flange 35 on the
housing. Electrical lead-in wires 36 extend through an opening in
the housing.
As will be understood, if magnetizing current is passed through
leads 36 to the solenoid 10, the resulting magnetic flux flows
through the housing 2, armature 18, and pole piece 6, and intends
to draw the armature to the right, as illustrated, into contact
with the pole piece. For any given position of the armature, the
force thus exerted is substantially proportional to the
magnetomotive force, which again is substantially proportional to
current as long as the saturation of the iron does not
significantly vary the reluctance of the magnetic circuit. If the
armature moves, the force increases as the surfaces 22 and 23
approach each other.
The device is intended primarily, however, for use in a
substantially stationary condition in which force is modulated
rather than position. This modulation may be accomplished by
varying the magnitude of a constant current or by varying the
average current as, for example, by duty cycle control of current
flowing through the solenoid.
Actuating rod 26 should be of a nonmagnetic material such, for
example, as stainless steel type 302 or 303, in order to minimize
any tendency of the flux to pass through the actuating rod into the
pole piece 6 which would tend to cause binding or friction in the
actuator.
The actuating rod 26 may be coupled to any device. For example, it
might actuate a valve or oppose the flyweights in a governor for
variable speed setting.
FIG. 2 illustrates a thruster which may be essentially the same as
or identical to that in FIG. 1 except for the structure of the
armature and the actuating rod or tappet which transmits the
movement or force of the armature to the exterior of the thruster.
This device comprises a housing 2, pole piece 6, solenoid 10,
bobbin 11, and O-ring 34 as described above. The armature 42 may be
essentially the same as that described above except that it has no
interior bore and the conical tip 22 terminates in a flat end
43.
The actuating rod 44 in this case is a tappet having a rounded
inner end 46 engageable by the end surface 43 of the armature and
having a flat head 47 at the exterior of the pole piece. This head
47 when biased by the armature may press against any desired
device.
FIG. 3 illustrates the application of the device of FIG. 2 to the
closing of a valve providing controllable resistance to flow of
fluid from a source or cavity. As shown there, the housing 2 is
mounted so that the pole piece 6 abuts a body or valve block 54
which defines a recess 55 into which the external boss 7 of the
pole piece is piloted. An O-ring 56 prevents leakage around the
boss 7. The recess 55 defines a valve chamber having an entrance 58
and containing a spherical valve member 59 which may engage a seat
60 at the end of the entrance passage 58. The head 47 of the
actuating rod 44 may bear against the sphere to urge it with
varying degrees of force against the seat 60. Fluid which passes
through the valve may exhaust through a drain or other exit passage
62. The solenoid may be held in place by a suitably attached
retaining ring 64. As will be apparent, if fluid is introduced
through the passage 58, the resistance to its escape will be a
function of the force exerted by the armature 42 and, therefore,
the average current going through the solenoid 10 of the valve
device may maintain the pressure communicating with the inlet 58 at
a particular desired value as a function of this current. If the
supply of fluid through passage 58 is limited, this regulation may
be accomplished with slight travel of valve member 59. The valve is
thus well-adapted to regulate a pressure to control further
hydraulic devices as a function of solenoid current.
FIG. 4 is a graph illustrating current force characteristics of a
device as illustrated. With a sufficiently wide air gap, as
illustrated in the curve labeled A, the relationship of force
exerted to current in a particular example is essentially linear.
As illustrated in curve B, with a much narrower air gap, the curve
is less linear because of the effect of saturation. However, above
the point C on the curve, the increment of force as a function of
current is substantially constant. There are two air gaps in
series, one at each end of the armature.
Among the advantages of the thruster device as illustrated herein
are the substantially constant or consistent relation of force to
current, a fast response to transients, and negligible hysteresis;
that is, variation of the force exerted between increasing and
decreasing current flows.
The particular thrusters illustrated are shown to scale and have a
housing about 11/2 inches in diameter and a solenoid of 600
turns.
The detailed description of the preferred embodiment of the
invention for the purpose of explaining the principles thereof is
not to be considered as limiting or restricting the invention,
since many modifications may be made by the exercise of skill in
the art.
* * * * *