Electromagnetic valve actuator for an internal combustion engine

Baker, Mark S.

Patent Application Summary

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 Number20030177989 10/366252
Document ID /
Family ID28045176
Filed Date2003-09-25

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

Application Number Filing Date Patent Number
60358561 Feb 21, 2002

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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