U.S. patent application number 10/366252 was filed with the patent office on 2003-09-25 for electromagnetic valve actuator for an internal combustion engine.
Invention is credited to Baker, Mark S..
Application Number | 20030177989 10/366252 |
Document ID | / |
Family ID | 28045176 |
Filed Date | 2003-09-25 |
United States Patent
Application |
20030177989 |
Kind Code |
A1 |
Baker, Mark S. |
September 25, 2003 |
Electromagnetic valve actuator for an internal combustion
engine
Abstract
An electromagnetic valve actuator for providing an actuation
force to open and close a valve. In one embodiment of the
invention, the valve is an intake and/or exhaust valve associated
with an internal combustion engine. In a preferred embodiment of
the invention, the valve actuator includes first and second
electromagnets spaced apart and arranged generally opposite one
another to define a tapered air gap therebetween. An actuator arm
is operatively coupled to the valve and is pivotally displaceable
within the air gap between a first operational position adjacent
the first electromagnet and a second operational position adjacent
the second electromagnetic. Selective activation of the
electromagnets causes the actuator arm to pivot between the first
and second operational positions to correspondingly open and close
the valve.
Inventors: |
Baker, Mark S.; (Delphi,
IN) |
Correspondence
Address: |
Woodard, Emhardt, Naughton,
Moriarty and McNett LLP
Bank One Center/Tower
111 Monument Circle, Suite 3700
Indianapolis
IN
46204-5137
US
|
Family ID: |
28045176 |
Appl. No.: |
10/366252 |
Filed: |
February 13, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60358561 |
Feb 21, 2002 |
|
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Current U.S.
Class: |
123/90.11 |
Current CPC
Class: |
F01L 9/20 20210101; F01L
2009/2109 20210101 |
Class at
Publication: |
123/90.11 |
International
Class: |
F01L 009/04 |
Claims
What is claimed is:
1. An electromagnetic valve actuator for displacing a valve between
an open position and a closed position along a travel axis,
comprising: first and second electromagnets; and an actuator arm
operatively coupled to the valve and pivotally displaceable between
a first operational position adjacent said first electromagnet and
a second operational position adjacent said second electromagnetic;
and wherein selective activation of said first and second
electromagnets causes said actuator arm to pivot between said first
and second operational positions to correspondingly displace the
valve between the open and closed positions.
2. The electromagnetic valve actuator of claim 1, wherein said
first and second electromagnets each define a magnetic attraction
surfaces, at least one of said magnetic attraction surfaces
arranged at an obtuse angle relative to the travel axis.
3. The electromagnetic valve actuator of claim 2, wherein each of
said magnetic attraction surfaces are arranged at an obtuse angle
relative to the travel axis.
4. The electromagnetic valve actuator of claim 1, wherein said
first and second electromagnets are disposed generally opposite one
another and spaced apart to define an air gap therebetween.
5. The electromagnetic valve actuator of claim 4, wherein said air
gap is tapered.
6. The electromagnetic valve actuator of claim 1, wherein the valve
is an intake valve or an exhaust valve of an internal combustion
engine.
7. The electromagnetic valve actuator of claim 6, further
comprising a mounting bracket for pivotally coupling said actuator
arm to the engine.
8. The electromagnetic valve actuator of claim 1, wherein said
actuator arm is at least partially formed of a permanent magnet
material to facilitate pivotal displacement of said actuator arm
between said first and second operational positions.
9. The electromagnetic valve actuator of claim 1, wherein said
actuator arm defines a channel sized to receive a stem portion of
the valve therein to pivotally engage said actuator arm to the
valve.
10. The electromagnetic valve actuator of claim 9, wherein said
actuator arm includes a yoke defining said channel.
11. The electromagnetic valve actuator of claim 10, wherein the
valve includes a pair of engaging members connected to the stem
portion of the valve and disposed on opposite sides of said
yoke.
12. The electromagnetic valve actuator of claim 11, wherein said
pair of engaging members define a first pair of opposing convex
surfaces, said yoke defining a second pair of oppositely facing
convex surfaces configured to rollingly engage said first pair of
opposing convex surfaces.
13. An electromagnetic valve actuator for displacing a valve
between an open position and a closed position along a travel axis,
comprising: an electromagnet having a magnetic attraction surface
arranged at an obtuse angle relative to the travel axis; and an
actuator arm operatively coupled to the valve and pivotally
displaceable between a first operational position arranged at an
angle relative to said magnetic attraction surface and a second
operational position arranged generally parallel to said magnetic
attraction surface; and wherein selective activation of said
electromagnet causes said actuator arm to pivot between said first
and second operational positions to correspondingly displace the
valve between the open and closed positions.
14. The electromagnetic valve actuator of claim 13, further
comprising a pair of electromagnets, each of said electromagnets
having a magnetic attraction surface, at least one of said magnetic
attraction surfaces being arranged at an obtuse angle relative to
the travel axis; and wherein said first operational position of
said actuator arm is arranged generally parallel to one of said
attraction surfaces, said second operational position of said
actuator arm being arranged generally parallel to another of said
attraction surfaces; and wherein selective activation of said
electromagnets causes said actuator arm to pivot between said first
and second operational positions to correspondingly displace the
valve between the open and closed positions.
15. The electromagnetic valve actuator of claim 14, wherein each of
said magnetic attraction surfaces are arranged at an obtuse angle
relative to the travel axis
16. The electromagnetic valve actuator of claim 14, wherein said
pair of electromagnets are disposed generally opposite one another
and spaced apart to define an air gap therebetween.
17. The electromagnetic valve actuator of claim 16, wherein said
air gap is tapered.
18. The electromagnetic valve actuator of claim 14, wherein said
actuator arm is at least partially formed of a permanent magnet
material to facilitate pivotal displacement of said actuator arm
between said first and second operational positions.
19. An electromagnetic valve actuator for displacing a valve
between an open position and a closed position along a travel axis,
comprising: an actuator arm operatively coupled to the valve and
pivotally displaceable between a first operational position and a
second operational position; and electromagnetic means for
pivotally displacing said actuator arm between said first and
second operational positions to correspondingly displace the valve
between the open and closed positions.
20. The electromagnetic valve actuator of claim 19, further
comprising means for pivotally coupling said actuator arm to the
valve.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims the benefit of Provisional
Application Serial No. 60/358,561 filed on Feb. 21, 2002, the
contents of which are hereby incorporated by reference in their
entirety.
FIELD OF THE INVENTION
[0002] The present invention generally relates to an
electromagnetic valve actuator system, and more specifically
relates to an electromagnetic valve actuator adapted to open and
close an intake valve and/or an exhaust valve of an internal
combustion engine.
BACKGROUND OF THE INVENTION
[0003] In conventional piston-type internal combustion engines, the
intake and exhaust valves are actuated by a camshaft that is
rotatably mounted within the engine block by a number of high-speed
bearings. The camshaft is mechanically coupled to the
intake/exhaust valves by an intermediate linkage system comprised
of a series of lifters, pushrods and rocker arms. The intermediate
linkage system serves to translate rotational movement of the
camshaft into linear movement of the intake/exhaust valves. In
addition to exhibiting a relatively high degree of complexity,
conventional cam-driven valve actuation systems require
high-precision parts which tends to increase manufacturing costs.
Moreover, the large number of interconnection points between the
various camshaft and linkage components leads to increased
frictional losses that correspondingly decrease engine efficiency
and reduce engine power output.
[0004] To address some of the drawbacks associated with
conventional cam-driven valve actuation systems, alternative
systems have been developed which use various types of
electromagnetic valve actuators. Such actuation systems typically
include one or more electromagnets that produce a magnetic
attraction force to effect the opening and closing of the
intake/exhaust valves. Electromagnetic valve actuation systems
offer greater control over cycling of the valves, particularly
during varying load requirements of the engine. Additionally,
electromagnetic valve actuation systems typically require a smaller
number of high-precision parts relative to conventional cam-driven
systems. Moreover, the decrease in mechanical complexity and the
reduction in the number of interconnection points tends to decrease
frictional losses which correspondingly increases engine efficiency
and engine power output. Furthermore, the oil pump capacity of
electromagnetic valve actuation systems is typically about one-half
that of conventional cam-driven systems.
[0005] However, prior attempts at developing electromagnetic valve
actuator systems have resulted in relatively low responsiveness of
valve actuation, particularly at high engine speeds. Additionally,
the air gap between the electromagnet(s) and the actuator plate is
relatively large, thereby tending to increase the size of
electromagnet required to produce the requisite amount of magnetic
attraction force necessary to open and close the valve.
[0006] Thus, there is a general need in the industry to provide an
improved electromagnetic valve actuator. The present invention
satisfies this need and provides other benefits and advantages in a
novel and unobvious manner.
SUMMARY OF THE INVENTION
[0007] The present invention is directed to an electromagnetic
valve actuator for use in an internal combustion engine. While the
actual nature of the invention covered herein can only be
determined with reference to the claims appended hereto, certain
forms of the invention that are characteristic of the preferred
embodiments disclosed herein are described briefly as follows.
However, it should be understood that other embodiments are also
contemplated as falling within the scope of the present
invention.
[0008] In one form of the present invention, an electromagnetic
valve actuator is provided for displacing a valve between an open
position and a closed position, including first and second
electromagnets and an actuator arm operatively coupled to the valve
and pivotally displaceable between a first operational position
adjacent the first electromagnet and a second operational position
adjacent the second electromagnetic. Activation of one of the first
and second electromagnets causes the actuator arm to pivot between
the first and second operational positions to correspondingly
displace the valve between the open and closed positions.
[0009] In another form of the present invention, an electromagnetic
valve actuator is provided for displacing a valve between an open
position and a closed position, including an electromagnet having a
magnetic attraction surface arranged at an obtuse angle relative to
the travel axis. An actuator arm is operatively coupled to the
valve and is pivotally displaceable between a first operational
position arranged at an angle relative to the magnetic attraction
surface and a second operational position arranged generally
parallel to the magnetic attraction surface. Activation of the
electromagnet causes the actuator arm to pivot between the first
and second operational positions to correspondingly displace the
valve between the open and closed positions.
[0010] In yet another form of the present invention, an
electromagnetic valve actuator is provided for displacing a valve
between an open position and a closed position, including an
actuator arm operatively coupled to the valve and pivotally
displaceable between a first operational position and a second
operational position, and an electromagnetic means for pivotally
displacing the actuator arm between the first and second
operational positions to correspondingly displace the valve between
the open and closed positions.
[0011] It is one object of the present invention to provide an
improved electromagnetic valve actuator.
[0012] Further objects, features, advantages, benefits, and aspects
of the present invention will become apparent from the drawings and
description contained herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a partial cross-sectional side view of an
electromagnetic valve actuator according to one form of the present
invention, as used in association with an intake valve and/or
exhaust valve of an internal combustion engine.
[0014] FIG. 2 is a partial cross-sectional end view of the
electromagnetic valve actuator illustrated in FIG. 1.
[0015] FIG. 3 is a top view of the electromagnetic valve actuator
illustrated in FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0016] For the purposes of promoting an understanding of the
principles of the present invention, reference will now be made to
the preferred embodiments illustrated in the drawings and specific
language will be used to describe the same. It will nevertheless be
understood that no limitation on the scope of the present invention
is intended, and any alterations or modifications in the disclosed
embodiments and further applications of the principles of the
present invention are contemplated as would normally occur to one
skilled in the art to which the present invention relates.
[0017] Referring to FIGS. 1-3, shown therein is an electromagnetic
valve actuator 10 according to one form of the present invention.
In one embodiment of the present invention, the electromagnetic
valve actuator 10 is used in association with a piston-type
internal combustion engine 12 to displace a valve 14 between an
open position and a closed position generally along a longitudinal
travel axis L.sub.1. The valve 14 is axially displaced relative to
a valve port 16 machined into the cylinder head 18 of the engine
12. As should be apparent to one of ordinary skill in the art, the
opening and closing of the valve 14 is controlled based upon the
particular operating cycle of the internal combustion engine
12.
[0018] When the valve 14 is in the open position, flow
communication is provided between the valve port 16 and an internal
combustion chamber 20. Likewise, when the valve 14 is in the closed
position, flow communication is shut-off between the valve port 16
and the internal combustion chamber 20. It should be understood
that the valve 14 may be either an intake valve adapted to control
the flow of a combustion mixture into the combustion chamber 20, or
an exhaust valve adapted to control the flow of combustion
by-products from the combustion chamber 20 to an exhaust system.
Additionally, although the electromagnetic valve actuator 10 has
been illustrated and described for use in association with an
internal combustion engine 12, it should be understood that other
applications of the electromagnetic valve actuator 10 are also
contemplated as falling within the scope of the present
invention.
[0019] The valve 14 is generally comprised of a valve seating
element 30 having a cross-section corresponding to the shape of the
valve port 16, and a valve stem 32 extending axially from the
seating element 30. The valve seating element 30 has a conical
surface 34 that sealingly engages a tapered valve seat surface 36
when the valve 14 is in a closed position to shut-off flow
communication between the valve port 16 and the internal combustion
chamber 20. The cylinder head 18 includes a valve guide 40 sized to
slidably receive the valve stem 32 therein to guide the valve 14
generally along the longitudinal travel axis L.sub.1. Further
details regarding the configuration of the intake/exhaust valve 14
would be readily know to one of skill in the art, and therefore
need not be expressly discussed herein.
[0020] The electromagnetic valve actuator 10 is generally comprised
of a pair of solenoids or electromagnets 50a, 50b, and an actuator
arm 60 disposed between the electromagnets 50a, 50b and operatively
coupled to the valve stem 32. As will be discussed in further
detail below, the actuator arm 60 is pivotally displaceable between
a first operational position adjacent the lower electromagnet 50b
and a second operational position adjacent the upper
electromagnetic 50a (as shown in FIG. 1). Selective activation of
the first and second electromagnets 50a, 50b creates a magnetic
attraction force that causes the actuator arm 60 to pivot between
the first and second operational positions to correspondingly
displace the valve 14 along the longitudinal travel axis L.sub.1
between the open and closed positions, respectively.
[0021] In one embodiment of the present invention, activation of
the electromagnet 50a exerts a magnetic attraction force onto the
actuator arm 60 to pivotally displace the actuator arm in the
direction of arrow A. Pivotal displacement of the actuator arm 60
in the direction of arrow A correspondingly exerts an axial force
onto the valve stem 32, which axially displaces the valve 14 in the
direction of arrow B to close the valve 14. Similarly, activation
of the electromagnet 50b exerts a magnetic attraction force onto
the actuator arm 60 to pivotally displace the actuator arm in the
direction of arrow C. Pivotal displacement of the actuator arm 60
in the direction of arrow C correspondingly exerts an axial force
onto the valve stem 32, which axially displaces the valve 14 in the
direction of arrow D to open the valve 14.
[0022] The electromagnets 50a, 50b each include a magnetic
attraction surface 52, 54, respectively. In a preferred embodiment
of the present invention, the magnetic attraction surfaces 52, 54
are disposed generally opposite one another and are spaced apart to
define an air gap G therebetween. The magnetic attraction surfaces
52, 54 are preferably angularly disposed relative to one another to
form a tapering air gap G therebetween. More specifically, the
magnetic attraction surfaces 52, 54 are preferably arranged in a
non-parallel manner so as to form an acute angle .alpha.
therebetween. In one embodiment of the invention, the acute angle
.alpha. falls within a range of about 5 degrees to about 45
degrees. In a more specific embodiment, the acute angle .alpha. is
about 25 degrees. However, it should be understood that the acute
angle .alpha. may take on other values, including angles less than
5 degrees and greater than 45 degrees.
[0023] It should also be understood that other arrangements of the
electromagnets 50a, 50b are also contemplated as falling within the
scope of the present invention. For example, in another embodiment
of the invention, the magnetic attraction surfaces 52, 54 may be
arranged in a substantially parallel arrangement relative to one
another, with the portion of the actuator arm 60 disposed within
the air gap G having oppositely facing surfaces that are angled
relative to one another so as to define a wedge shape. In this
embodiment, the angled engaging surfaces of the actuator arm 60
would be positioned in abutment against respective magnetic
attraction surfaces 52, 54 of the electromagnets 50a, 50b as the
actuator arm 60 is pivotally displaced between the first and second
operational positions. In yet another embodiment of the invention,
the electromagnets 50a, 50b may be disposed on opposite sides of
the longitudinal travel axis L.sub.1 of the valve 14. In this
embodiment, the actuator arm 60 would be rockably mounted to the
valve stem 32 such that opposite portions of the actuator arm 60
would be positioned in abutment against respective magnetic
attraction surfaces 52, 54 of the electromagnets 50a, 50b as the
actuator arm 60 is pivotally displaced between the first and second
operational positions.
[0024] In a preferred embodiment of the invention, the tapering air
gap G is substantially symmetrical relative to a transverse axis T
arranged perpendicular to the longitudinal travel axis L.sub.1 of
the valve 14. In this manner, both of the magnetic attraction
surfaces 52, 54 are arranged at an obtuse or non-perpendicular
angle relative to the longitudinal travel axis L.sub.1 of valve 14.
However, it should be understood that other geometric arrangements
of the electromagnets 50a, 50b are also contemplated as falling
within the scope of the present invention. For example, in an
another embodiment of the invention, only one of the magnetic
attraction surfaces 52, 54 is arranged at an obtuse angle relative
to the longitudinal travel axis L.sub.1, with the other magnetic
attraction surfaces 52, 54 being arranged generally perpendicular
to the longitudinal travel axis L.sub.1.
[0025] Each of the electromagnets 50a, 50b are electrically coupled
to a controller (not shown) via electrical leads or terminals 56,
58, respectively. The controller (not shown) serves to selectively
supply power to the electromagnets 50a, 50b to control the
activation/deactivation of the magnetic attraction force field. The
illustrated embodiment of the electromagnets 50a, 50b is one
example of an electromagnet suitable for use in association with
the electromagnetic valve actuator 10. However, it should be
understood that other suitable electromagnets are also contemplated
as would occur to one of ordinary skill in the art. Additionally,
although the electromagnets 50a, 50b are illustrated as having a
cylindrical shape, it should be understood that other shapes are
also contemplated as falling within the scope of the present
invention, including elliptical, oblong, square, or rectangular
shapes.
[0026] The actuator arm 60 extends generally along a second
longitudinal axis L.sub.2 and is comprised of a drive portion 62,
an intermediate portion 64, and a distal end portion 66. The distal
end portion 66 is adapted to interface and co-act with the valve 14
to displace the valve 14 between the open and closed positions upon
the pivotal displacement of the actuator arm 60 between the first
and second operational positions. In one embodiment of the present
invention, the distal end portion 66 is configured as a yoke,
including a pair of forks 68a, 68b disposed generally opposite one
another and spaced apart to define a channel 70 therebetween. The
yoke channel 70 is sized to receive a portion of the valve stem 32
therein to pivotally couple the actuator arm 60 to the valve
14.
[0027] The drive portion 62 of the actuator arm 60 is positioned
within the air gap G between the electromagnets 50a, 50b and
includes an upper magnetic engagement surface 72 and a lower
magnetic engagement surface 74. In one embodiment of the present
invention, the size and shape of the upper and lower magnetic
engagement surfaces 72, 74 correspond to the size and shape of the
magnetic attraction surface 52, 54 of the electromagnets 50a, 50b.
In this manner, the upper and lower magnetic engagement surfaces
72, 74 will be arranged in a substantially parallel and abutting
relationship relative to the magnetic attraction surface 52, 54,
respectively, when the actuator arm 60 is positioned in the first
and second operational positions. A pair of pivot pins 75a, 75b
extend from the drive portion 62 of the actuator arm 60 in opposite
directions and are aligned generally along a pivot axis P. The
function of the pivot pins 75a, 75b will be discussed below.
[0028] At least the drive portion 62 of the actuator arm 60 is
formed of a magnetizable material to facilitate magnetic attraction
and/or repulsion between the magnetic engagement surfaces 72, 74
and the magnetic attraction surface 52, 54 during the selective
activation of a respective one of the electromagnets 50a, 50b. In
one embodiment of the present invention, the magnetizable material
is a steel material, such as, for example, cold-rolled steel.
However, other suitable magnetizable materials are also
contemplated as would occur to one of skill in the art. In another
embodiment of the present invention, the drive portion 62 of the
actuator arm 60 is at least partially formed of a magnet material
to strengthen the magnetic attraction force between the magnetic
engagement surfaces 72, 74 and the magnetic attraction surface 52,
54 to further facilitate pivotal displacement of the actuator arm
60 between the first and second operational positions. In one
embodiment, the magnet material is a permanent magnet material,
such as, for example, a rare earth magnet. However, other suitable
magnet materials are also contemplated as would occur to one of
skill in the art. As should be appreciated, if the drive portion 62
is at least partially formed of a magnet material, the polarity of
the magnet material and the adjacent electromagnet 50a, 50b may be
opposite one another so as to generate a magnetic attraction force
and/or may be the same so as to generate a magnetic repulsion
force.
[0029] In one embodiment of the present invention, the forks 68a,
68b of the yoke 66 each define a pair of oppositely facing upper
and lower convex surfaces 76, 78. The stem portion 32 of the valve
14 includes a pair of upper and lower engaging members 80a, 80b
disposed on opposite sides of the yoke 66. In the illustrated
embodiment of the invention, the valve stem 32 defines a lower
shoulder 82 for supporting the lower engaging member 80b. A lock
nut 84 or any other suitable fastener may be threaded onto the
distal end portion of the valve stem 32 to retain the upper
engaging member 80a. However, it should be understood that the
engaging members 80a, 80b may be coupled to the valve stem 32 by
any suitable means that would occur to one of skill in the art.
[0030] In one embodiment of the invention, the upper and lower
engaging members 80a, 80b define a pair of opposing convex surfaces
86, 88 that preferably have substantially the same radius of
curvature as the convex surfaces 76, 78 of the yoke 66. Notably, as
the actuator arm 60 is pivotally displaced between the first and
second operational positions, the convex surfaces 76, 78 of the
yoke 66 will rollingly engage the convex surfaces 86, 88 defined by
the upper and lower engaging members 80a, 80b. Such rolling
engagement between the abutting surfaces of the yoke forks 68a, 68b
and the upper and lower engaging members 80a, 80b tends to minimize
frictional losses and wear associated with the repeated cycling of
the valve actuator 10 and the valve 14.
[0031] In one embodiment of the invention, the actuator arm 60 is
pivotally supported by a mounting bracket 90. The mounting bracket
90 is preferably attached to a relatively flat surface of the
cylinder head 18 to pivotally couple the actuator arm 60 to the
engine 12. The mounting bracket 90 is generally comprised of a pair
of vertical support plates 92a, 92b, a horizontal support plate 94,
and a pair of base rails 96a, 96b. The horizontal support plate 94
extends between the upper ends of the vertical support plates 92a,
92b to provide support and stabilization to the mounting bracket
90. The base rails 96a, 96b extend from the bottom ends of the
vertical support plates 92a, 92b to provide a means for securely
and stably attaching the mounting bracket 90 to a substrate, such
as, for example, the cylinder head 18.
[0032] The vertical support plates 92a, 92b, the horizontal support
plate 94, and the base rails 96a, 96b are integrally connected to
form a substantially rigid mounting structure. In one embodiment,
the components of the mounting bracket 90 are interconnected by
welding; however, other methods of interconnection are also
contemplated, such as, for example, by fastening. The vertical
support plates 92a, 92b each define an opening 98a, 98b sized to
respectively receive the pivot pins 75a, 75b of the actuator arm 60
therein. The mounting bracket 90 thereby serves to pivotally
support the actuator arm 60 to allow the actuator arm 60 to pivot
about a pivot axis P and to interact with and correspondingly
displace the valve 14 between open and closed positions. Although a
specific embodiment of a mounting bracket 90 has been illustrated
and described herein for pivotally supporting the actuator arm 60,
it should be understood that other types and configurations of
mounting brackets are also contemplated as would occur to one of
skill in the art.
[0033] Having described the various components of the
electromagnetic valve actuator 10, reference will now be made to
the operation of the same according to one embodiment of the
present invention. Referring to FIG. 1, the valve 14 is shown in a
closed position, with the valve seating element 30 tightly engaged
against the valve seat 36. However, when the electromagnet 50b is
energized, the magnetic attraction force generated by the
electromagnet 50b will attract the drive portion 62 of the actuator
arm 60. In turn, the actuator arm 60 will be pivotally displaced
about the pivot axis P in the direction of arrow C until the lower
engagement surface 74 of actuator arm 60 is engaged against the
magnetic attraction surface 54 of electromagnet 50b. Such pivotal
movement of the actuator arm 60 correspondingly displaces the valve
14 along the longitudinal travel axis L.sub.1 in the direction of
arrow D toward the open position, thereby disengaging the valve
seating element 30 from the valve seat 36.
[0034] After a predetermined period of time, the electromagnet 50b
is de-energized and the electromagnet 50a is energized. The
magnetic attraction force generated by the electromagnet 50a will
attract the drive portion 62 of the actuator arm 60. In turn, the
actuator arm 60 will be pivotally displaced about the pivot axis P
in the direction of arrow A until the upper engagement surface 72
of actuator arm 60 is engaged against the magnetic attraction
surface 52 of electromagnet 50a. Such pivotal movement of the
actuator arm 60 will correspondingly displace the valve 14 along
the longitudinal travel axis L.sub.1 in the direction of arrow B
toward the closed position, thereby tightly engaging the valve
seating element 30 against the valve seat 36. The cycle is then
repeated by de-energizing the electromagnet 50a and re-energizing
the electromagnet 50b. As should be apparent to one of skill in the
art, the timing associated with the selective
activation/deactivation of the electromagnets 50a, 50b to
correspondingly open and close the valve 14 is based upon the
particular operating cycle of the internal combustion engine
12.
[0035] In another embodiment of the invention, a compression spring
(not shown) may be disposed about the valve stem 32 and positioned
between the lower engaging member 80b and the cylinder head 18 to
exert an upward biasing force onto the valve 12. The compression
spring would serve to position the valve 12 in a closed position in
the event that neither of the electromagnets 50a, 50b are
energized. The compression spring would effectively act as a
fail-safe device to close the valve 12 if control power to the
electromagnets 50a, 50b were interrupted and/or in the event of a
system failure. It should be noted, however, that the biasing force
exerted by the compression spring should be selected so as to avoid
interference with proper opening of the valve 14.
[0036] The electromagnetic valve actuator 10 illustrated and
described above offers certain advantages with respect to prior
electromagnetic valve actuators. For example, the use of a
pivotally-displaceable actuator arm 60 to open and close the valve
14 correspondingly increases responsiveness of valve actuation.
This is at least partially the result of the leverage provided by
the actuator arm 60. As should be apparent, the actuation speed of
the yoke portion 66 will be multiplied relative to the drive speed
of the drive portion 62. This increase in speed is a function of
the distance d.sub.1 from the pivot axis P to the approximate
center of the yoke 66, and the distance d.sub.2 from the pivot axis
P to the approximate center of the drive portion 62 (corresponding
to the approximate center of the electromagnets 50a, 50b). In the
illustrated embodiment of the present invention, the distance
d.sub.1 is approximately 2.5 times that of the distance d.sub.2. As
a result, the actuation speed of the yoke portion 66 will be
multiplied by approximately 2.5 relative to the drive speed of the
drive portion 62.
[0037] Another advantage provided by the electromagnetic valve
actuator 10 over prior electromagnetic actuators is that the width
of the air gap between the electromagnets required to achieve a
certain distance of valve travel is significantly reduced. For
example, in the illustrated embodiment of the present invention,
the average width w of the air gap G is approximately two-fifths of
the corresponding distance of travel of the valve 14 along the
longitudinal travel axis L.sub.1. Since the strength of the
magnetic attraction force required to displace the actuator arm 60
between the first and second operation positions is proportional to
the width of the air gap between the electromagnets, the strength
and size of the electromagnets 50a, 50b can be significantly
reduced relative to the electromagnets used in association with
prior electromagnetic actuators.
[0038] While the invention has been illustrated and described in
detail in the drawings and foregoing description, the same is to be
considered as illustrative and not restrictive in character, it
being understood that only the preferred embodiments have been
shown and described and that all changes and modifications that
come within the spirit of the invention are desired to be
protected.
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