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1. WO2020117880 - SYSTÈME ÉLECTROMAGNÉTIQUE POUR COMMANDER LE MODE DE FONCTIONNEMENT D'UN ENSEMBLE D'ACCOUPLEMENT SANS FRICTION, ET ACCOUPLEMENT ET ENSEMBLE DE COMMANDE MAGNÉTIQUE LE COMPRENANT

Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique

[ EN ]

ELECTROMAGNETIC SYSTEM FOR CONTROLLING THE OPERATING MODE OF A NONFRICTION COUPLING ASSEMBLY AND COUPLING AND MAGNETIC CONTROL

ASSEMBLY HAVING SAME

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. provisional application Serial No.

62/774,957, filed December 4, 2018, the disclosure of which is hereby incorporated in its entirety by reference herein.

TECHNICAL FIELD

[0002] This invention generally relates to systems for controlling the operating mode of a non-friction coupling assembly and coupling and control assemblies having same and, in particular, to such systems which are electromagnetically operated and magnetically controlled.

OVERVIEW

[0003] A typical one-way clutch (OWC) consists of an inner ring, an outer ring and a locking device between the two rings. The one-way clutch is designed to lock in one direction and to allow free rotation in the other direction. Two types of one-way clutches often used in vehicular, automatic transmissions include:

]0004j Roller type which consists of spring loaded rollers between die inner and outer races of the one-way clutch. (Roller type is also used without springs on some applications); and

[0005] Sprag type which consists of asymmetrically shaped wedges located between the inner and outer races of the one-way clutch.

[0006] The one-way clutches are typically used in the transmission to prevent an interruption of drive torque (i.e., power flow) during certain gear shifts and to allow engine braking during coasting.

[0007] Controllable or selectable one-way clutches (i.e., OWCs) are a departure from traditional one-way clutch designs. Selectable OWCs add a second set of locking members in combination with a slide plate. The additional set of locking members plus the slide plate adds multiple functions to the OWC. Depending on the needs of the design, controllable OWCs are capable of producing a mechanical connection between rotating or stationary shafts in one or both directions. Also, depending on the design, OWCs are capable of overrunning in one or both directions. A controllable OWC contains an externally controlled selection or control mechanism. Movement of this selection mechanism can be between two or more positions which correspond to different operating modes.

U.S. Patent No. 5,927,455 discloses a bi-directional overrunning pawl-type clutch, U.S. Patent No. 6,244,965 discloses a planar overrunning coupling, and U.S. Patent No. 6,290,044 discloses a selectable one-way clutch assembly for use in an automatic transmission.

[0009] U.S. Patent Nos. 7,258,214 and 7,344,010 disclose overrunning coupling assemblies, and U.S. Patent No. 7,484,605 discloses an overrunning radial coupling assembly or clutch.

[0010] A properly designed controllable OWC can have near-zero parasitic losses in the

“off” state. It can also be activated by electro-mechanics and does not have either the complexity or parasitic losses of a hydraulic pump and valves.

[0011] Other related U.S. patent publications include; 2011/0140451; 2011/0215575

2011/0233026; 2011/0177900; 2010/0044141; 2010/0071497; 2010/0119389; 2010/0252384

2009/0133981; 2009/0127059; 2009/0084653; 2009/0194381; 2009/0142207; 2009/0255773 2009/0098968; 2010/0230226; 2010/0200358; 2009/0211863; 2009/0159391; 2009/0098970 2008/0223681; 2008/0110715; 2008/0169166; 2008/0169165; 2008/0185253; 2007/0278061 2007/0056825; 2006/138777; 2006/0185957; 2004/0110594; and the following U.S. Patent Nos

7,942,781; 7,806,795; 7,690,455; 7,491,151; 7,484,605; 7,464,801; 7,275,628; 7,256,510 7,223,198; 7,198,587, 7,093,512; 6,953,409; 6,846,257; 6,814,201; 6,503,167; 6,193,038; 4,050,560 4,340,133; 5,597,057; 5,918,715; 5,638,929; 5,362,293; 5,678,668; 5,070,978; 5,052,534 5,387,854; 5,231,265; 5,394,321; 5,206,573; 5,453,598; 5,642,009; 6,075,302; 6,982,502 7,153,228; 5,924,510; and 5,918,715.

[0012] Mechanical forces that are due to local or distant magnetic sources, i.e. electric currents and/or permanent magnet (PM) materials, can be determined by examination of the magnetic fields produced or“excited” by the magnetic sources. A magnetic field is a vector field indicating at any point in space the magnitude and direction of the influential capability of the local or remote magnetic sources. The strength or magnitude of the magnetic field at a point within any region of interest is dependent on the strength, the amount and the relative location of the exciting magnetic sources and the magnetic properties of the various mediums between the locations of the exciting sources and the given region of interest. By magnetic properties one means material characteristics that determine“how easy” it is to, or“how low” a level of excitation is required to, “magnetize” a unit volume of the material, that is, to establish a certain level of magnetic field strength. In general, regions which contain iron material are much easier to“magnetize” in comparison to regions which contain air or plastic material.

[0013] Magnetic fields can be represented or described as three-dimensional lines of force, which are closed curves that traverse throughout regions of space and within material structures.

When magnetic“action” (production of measurable levels of mechanical force) takes place within a magnetic structure these lines of force are seen to couple or link the magnetic sources within the structure. Lines of magnetic force are coupled/linked to a current source if they encircle all or a portion of the current path in the structure. Force lines are coupled/linked to a PM source if they traverse the PM material, generally in the direction or the anti-direction of the permanent magnetization. Individual lines of force or field lines, which do not cross one another, exhibit levels of tensile stress at every point along the line extent, much like the tensile force in a stretched“rubber band,” stretched into the shape of the closed field line curve. This is the primary method of force production across air gaps in a magnetic machine structure.

[0014] One can generally determine the direction of net force production in portions of a magnetic machine by examining plots of magnetic field lines within the structure. The more field lines (i.e. the more stretched rubber bands) in any one direction across an air gap separating machine elements, the more“pulling” force between machine elements in that given direction.

[0015] Metal injection molding (MIM) is a metalworking process where finely-powdered metal is mixed with a measured amount of binder material to comprise a‘feedstock’ capable of

being handled by plastic processing equipment through a process known as injection mold forming. The molding process allows complex parts to be shaped in a single operation and in high volume. End products are commonly component items used in various industries and applications. The nature of MIM feedstock flow is defined by a physics called rheology. Current equipment capability requires processing to stay limited to products that can be molded using typical volumes of 100 grams or less per“shot” into the mold. Rheology does allow this“shot” to be distributed into multiple cavities, thus becoming cost-effective for small, intricate, high-volume products which would otherwise be quite expensive to produce by alternate or classic methods. The variety of metals capable of implementation within MIM feedstock are referred to as powder metallurgy, and these contain the same alloying constituents found in industry standards for common and exotic metal applications. Subsequent conditioning operations are performed on the molded shape, where the binder material is removed and the metal particles are coalesced into the desired state for the metal alloy.

[0016] For purposes of this application, the term“coupling” should be interpreted to include clutches or brakes wherein one of the plates is drivably connected to a torque delivery element of a transmission and the other plate is drivably connected to another torque delivery element or is anchored and held stationary with respect to a transmission housing. The terms“coupling,”“clutch” and“brake” may be used interchangeably.

[0017] A number of magnetically and electromagnetical!y actuated clutches arc disclosed by the prior art such as the following U.S. Patent documents: 2018/0202502; 5,996,758; 9,732,809; 8,418,825; 9,097,299; 10,024,370; 9,127,730; 9,366,298; 9,739,322; 9,915,301; 2017/0248174; 2017/0138414; 2018/0094677; 2016/0160941; 2016/0252142; and 2019/0323568.

[0018] Many of such systems seek to reduce frictional losses that are present in actuation systems that act on locking elements within a rotating clutch member.

[0019] A magnetic circuit is made up of one or more closed loop paths containing a magnetic flux. The flux is usually generated by permanent magnets or electromagnets and confined to the path by magnetic cores consisting of ferromagnetic materials like iron, although there may be air gaps or other material in the path.

[0020] Similar to the way that electromotive force (EMF) drives a current of electrical charge in electrical circuits, magnetomotive force (MMF)‘drives’ magnetic flux through magnetic circuits.

[0021] The unit of magnetomotive force is the ampere-lum (At) represented by a steady, direct electric current of one ampere flowing in a single-tum loop of electrically conducting material m a vacuum.

[0022] Magnetic flux always forms a closed loop, but the path of the loop depends on the reluctance of the surrounding materials. It is concentrated around the path of least reluctance. Air and vacuum have high reluctance, while easily magnetized materials such as soft iron have low reluctance. The concentration of flux in low-reluctance materials forms strong temporary poles and causes mechanical forces that tend to move the materials towards regions of higher flux so it is always an attractive force (pull). If a permanent magnet is used as a magnetic circuit component in the loop, a repulsive force (i.e, push) can be generated.

[0023] As described in U.S. Patent document 2013/0015033, a magnetic circuit used to engage a coupling device may be weakened by leakage of magnetic flux along various paths. The presence of this flux pathway (or leakage circuit) drains magnetic flux from an interface thereby reducing the flux density at the interface and the attractive force. Such attractive forces need to be maximized in many situations.

SUMMARY OF EXAMPLE EMBODIMENTS

[0024] An object of at least one embodiment of the present invention is to provide an electromagnetic system for controlling the operating mode of a non-friction coupling assembly and coupling and magnetic control assembly having same wherein the magnetic attractive force on a ferromagnetic or magnetic locking element is maximized by increasing the flux density at the interface between the locking element and an electromagnetic source and decreasing any flux leakage.

[0025] In carrying out the above object and other objects at least one embodiment of the present invention, an electromagnetic system for controlling the operating mode of a non-friction coupling assembly is provided. The assembly includes first and second coupling members supported for a rotation relative to one another about a common axis. The first and second coupling members include coupling first and second faces, respectively, in close-spaced opposition with one another. The second coupling member has a third face spaced from the second face. The second lace has a pocket. The first face has a set of locking formations and the third face has first and second spaced passages in communication with the pocket. The system includes magnetic circuit components including a ferromagnetic or magnetic element received within the pocket in a first position and projecting outwardly from the pocket to a second position. The element controls the operating mode of the coupling assembly. A stationary electromagnetic source includes at least one excitation coil which generates a magnetic field between poles of the source when the at least one coil is supplied with current. Ferromagnetic or magnetic first and second inserts are received and retained within the first and second spaced passages, respectively, of the second coupling member. The first and second inserts are in closed-spaced opposition across first and second air gaps, respectively, with the first and second poles, respectively, of the electromagnetic source. The first and second inserts are in close spaced opposition across third and fourth air gaps, respectively, with first and second spaced positions, respectively, of the element. The electromagnetic source, the inserts, the air gaps and the element make up a closed loop path containing magnetic flux so that the element moves between the first and second spaced positions when the at least one coil is supplied with current.

[0026] The first and third faces may be oriented to face axially in a first direction along the rotational axis and the second lace may be oriented to lace axially in a second direction opposite the first direction along the rotational axis.

[0027] The electromagnetic source may further include an annular ring housing having an annular recess in which the at least one coil is located. The housing maybe axially symmetric about the rotational axis. The magnetic field may be a generally circular magnetic field.

[0028] The housing may have a generally C-shaped cross-section.

[0029] The element may be a locking element which prevents relative rotation of the first and second coupling members with respect to each other in at least one direction about the rotational axis.

[0030] The locking element may be an injection molded stmt.

[0031] The system may further include a return biasing member to urge the element to a return position which corresponds to either the first position or the second position of the element.

[0032] The first, second and third faces may be generally annular and extend generally radially with respect to the axis.

[0033] The coupling assembly may be a clutch assembly and the first and second faces may be clutch faces.

[0034] The at least one coil may have a circumference wherein the inserts may comprise magnetic pole pieces which cover substantially the entire circumference of the at least one coil.

[0035] The second coupling member may be made of non-ferrous/non-magnetic material.

[0036] A plurality of coils may generate the magnetic field.

[0037] Further in carrying out the above object and other objects of at least one embodiment of the present invention, a coupling and magnetic control assembly is provided. First and second coupling members are supported for a rotation relative to one another about a common axis. The first and second coupling members include coupling first and second faces, respectively, in closespaced opposition with one another. The second coupling member has a third face spaced from the second face. The second face has a pocket. The first face has a set of locking formations and the third face has first and second spaced passages in communication with the pocket. The assembly includes magnetic circuit components including a ferromagnetic or magnetic element received within the pocket in a first position and projecting outwardly from the pocket in a second position. The element controls the operating mode of the coupling assembly. A stationary electromagnetic source includes at least one excitation coil which generates a magnetic field between poles of the source when the at least one coil is supplied with current. Ferromagnetic or magnetic first and second inserts are received and retained within the first and second spaced passages, respectively, of the second coupling member. The first and second inserts are in close-spaced opposition across first and second air gaps, respectively, with the first and second poles, respectively, of the electromagnetic source. The first and second inserts are in close-spaced opposition across third and fourth air gaps, respectively, with first and second spaced portions, respectively, of the element. The electromagnetic source, the inserts, the air gaps and the element make up a closed loop path containing magnetic flux so that the element moves between the first and second positions when the at least one coil is supplied with current.

[0038] The first and third faces may be oriented to face axially in a first direction along the rotational axis and the second face may be oriented to face axially in a second direction opposite the first direction along the rotational axis.

[0039] The electromagnetic source may further include an annular ring housing having an annular recess in which the coil is located. The housing may be axially symmetric about the rotational axis. The magnetic field may be a generally circular magnetic field.

[0040] The housing may have a generally C-shaped cross-section.

[0041] The element may be a locking element which prevents relative rotation of the first and second coupling members with respect to each other in at least one direction about the rotational axis.

[0042] The locking element may be an injection molded strut.

[0043] The assembly may further include a return biasing member to urge the element to a return position which corresponds to either the first position or the second position of the element

[0044] The first, second and third faces may be generally annular and extend generally radially with respect to the axis.

[0045] The coupling assembly may be a clutch assembly and the first and second faces may be clutch faces.

[0046] The at least one coil may have a circumference wherein the inserts may comprise magnetic pole pieces which cover substantially the entire circumference of the at least one coil.

[0047] The second coupling member may be made of non-ferrous/non-magnetic material.

[0048] A plurality of coils may generate the magnetic field.

BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 is a side sectional schematic view of a coupling and magnetic control assembly constructed in accordance with at least one embodiment of the present invention and showing magnetic flux lines when a coil of a stationary electromagnetic source is supplied with current;

[0050] Figure 2 is a perspective, schematic view of a portion of the assembly of Figure 1 and particularly showing various air gaps between various magnetic circuit components;

[0051] Figure 3 is a top plan view, partially broken away, of the second coupling member or pocket plate to show where the magnetic pole pieces are to be fit or inserted within the plate;

[0052] Figure 4 is a bottom view, partially broken away, of the pocket plate and further illustrating where the circular magnetic field generated by the electromagnetic source points up and down with respect to the pole pieces;

[0053] Figure 5 is a side perspective schematic view of the electromagnetic source which is capable of generating the circular magnetic fields of Figure 4 when a coil contained in an annular recess of the annular housing of the source is energized by current;

[0054] Figure 6 is a view, partially broken away and in cross section, of the coupling and magnetic control assembly constructed in accordance with a second embodiment of the present invention;

|00S5] Figure 7 is an enlarged view of a portion of the assembly of Figure 6 showing a scale and magnetic field lines due to coil currents in an electromagnetic source of the assembly;

[0056] Figure 8 is a schematic view, partially broken away, of the pocket plate and locking member of Figure 6 with a biasing spring and pole pieces shown by phantom lines;

[0057] Figure 9 is a view, similar to the view of Figure 8, but without the magnetic circuit components or the spring of Figure 8;

[0058] Figure 10 is a perspective schematic view of the notch plate of Figure 6;

[0059] Figure 11 is perspective schematic view of the assembly of Figure 6 but without an electromagnetic source;

[0060] Figure 12 is a perspective schematic view of the electromagnetic source of Figure 6; and

[0061] Figure 13 is a perspective, schematic view of the assembly of Figure 6 without the notch plate of Figure 10 and without the pocket plate and return spring.

DETAILED DESCRIPTION

[0062] As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be inleipreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.

[0063] Referring now to Figures 1-5, there is illustrated a planar, coupling and magnetic control assembly, generally indicated at 11. The assembly 11 includes a first coupling member, generally indicated at 10, which may comprise a notch plate or member having a first coupling face

12.

[0064] The assembly 11 may include a non-ferrous, non-magnetic pocket plate or second member, generally indicated at 14, which includes a second coupling face 16 in close-spaced opposition with the first coupling face 12, when the members 10 and 14 are assembled and held

together by a locking or snap ring 18. At least one of the members 10 and 14 is mounted for rotation about a common axis 20 (Figure 5).

[0065] The second coupling member 14 also includes third face 22 spaced from the second face 16. The third face 22 has first and second spaced passages 25 and 23 which extend through the second coupling member 14 in communication with a pocket 24 formed in the second face 16.

[0066] The pocket 24 preferably is a T-shaped recess or pocket 24 as best shown in Figure 3.

The recess 24 defines a load bearing first shoulder. The first coupling face 12 of the notch plate 10 has a plurality of recesses or notches (not shown in the first embodiment, but shown in the second embodiment of the notch plate 110 in Figure 10). Each notch of the notches defines a load-bearing second shoulder. While only a single pocket 24 is shown, it is to be understood that a plurality of pockets 24 (and stmts 26) are preferred.

[0067] An electromagnetic system for controlling the operating mode of the coupling assembly includes a plurality of magnetic circuit components including a ferro-magnetic element or a locking stmt, generally included at 26, extendable between the coupling faces 12 and 16 of the member 10 and the member 14, respectively, when the members 10 and 14 are assembled and held together.

[0068] The element 26 may comprise a ferromagnetic locking element or stmt movable between first and second positions. The first position (not shown) is characterized by abutting engagement of the locking element 26 with a load-bearing shoulder (not shown) of the member 10 and the shoulder of the pocket 24 formed in an end wall of the second member 14. The second position (solid lines in Figures 1 and 2) is characterized by non-abutting engagement of the locking element 26 with a load-bearing shoulder of at least one of the members 10 and 14. A return biasing member or spring (not shown in the first embodiment, but shown in the second embodiment at 129) may be positioned under each of the struts 26 to urge its stmt 26 to a return position which corresponds to the uncoupling position of the stmt 26.

[0069] The electromagnetic system also includes a stationary electromagnetic source, generally indicated at 31, including at least one excitation coil 33 which is at least partially surrounded by a generally C-shaped (in cross-section) annular ring housing part 35. Instead of a single coil a plurality of similar coils could be provided to feed MMF into the core plates. In this embodiment, the coils would each wrap around a section of the core with the axes of the coils pointing in the direction of the field through the core. When the at least one coil 33 is energized (supplied with current), an axial symmetric, generally circular magnetic field (indicated by phantom lines in Figure 1) loops out of the housing part 35 at a north pole of the housing part 35, through a magnetic insert or pole piece 37, into a first portion of the strut 26, out a second portion of the strut, through another insert or pole piece 39 and back into the housing part 35 at a south pole of the housing part 35.

[0070] The pole pieces 37 and 39 are inserted into the bottom of the pocket 24 through the third face 22 and are received and retained within the first and second passages 25 and 23, respectively, and are in close-spaced opposition with the north and south poles, respectively, of the housing part 35.

[0071] The electromagnetic source 31, the element 26, the inserts 37 and 39, the air gaps between the inserts 37 and 39 and the element 26 and the air gaps between the source 31 and the inserts 37 and 39 make up a closed loop path containing magnetic flux so that the element 26 moves between its coupling and uncoupling positions when the coil 33 is supplied with current The pole pieces 37 and 39 direct the magnetic field into the strut 26 to attract (or repel) the strut 26 and move the strut 26 into an engaged (or disengaged) position.

[0072] Referring now to Figure 4, there is illustrated by phantom lines 41 an outwardly pointing (out of the page), circular magnetic field at the third face 22 in which the insert 39 is located. Phantom lines 43 illustrate an inwardly pointing (into the page), circular magnetic field in which insert 37 is located at the third face 22 of the second coupling member 14. The source 31 of Figure 5 directs a magnetic field at the back of the pocket plate 14 when the coil 33 is energized. The resulting magnetic field permeates into the pole pieces 37 and 39 and the strut 26.

[0073] The number of Amp-turns required to generate a mechanical force to move the strut 26 between coupling and uncoupling positions is a function of the size of the“Air Gaps” of Fi gure 2. Consequently, the air gaps should be made as small as possible to avoid leakage of magnetic flux in

order to minimize the number of Amp-tums required to generate the force necessary to move the strut 26 especially at high clutch member RPM (greater than 5k RPM).

[0074] Referring now to Figures 6-13, there is illustrated a second embodiment of a planar, coupling and magnetic control assembly, generally indicated at 111. The assembly 11 1 includes a first coupling member, generally indicated at 110, which may comprise a notch plate or member having a first coupling face 112. The parts or components of the second embodiment which are the same or similar to the parts or components of the first embodiment in either structure or function have the same reference number but one preceded by the number“1”.

[0075] The assembly 11 1 may include a non-ferrous, non-magnetic pocket plate or second member, generally indicated at 114, which includes a second coupling face 116 in close-spaced opposition with the first coupling face 112, when the members 110 and 114 are assembled and held together by a locking or snap ring 118. At least one of the members 110 and 114 is mounted for rotation about a common axis 120 (Figures 10 and 12).

[0076] The second coupling member 114 also includes third face 122 spaced from the second face 116. The third lace 122 has first and second spaced passages 125 and 123 which extend through the second coupling member 114 in communication with a pocket 124 formed in the second face 1 16.

[0077] The pocket 124 preferably is a T-shaped recess or pocket 124 as best shown in

Figures 8 and 9. The recess 124 defines a load bearing first shoulder. The first coupling face 112 of the notch plate 110 has a plurality of recesses or notches 113. Each notch 113 of the notches defines a load-bearing second shoulder. While only a single pocket 124 is shown in Figures 6-9, it is to be understood that a plurality of pockets 124 (and struts 126) are preferred as shown in Figure 13.

[0078] An electromagnetic system for controlling the operating mode of the coupling assembly 111 includes a plurality of magnetic circuit components including a ferro-magnetic element or a locking strut, generally included at 126, extendable between the coupling faces 112 and 116 of the member 110 and the member 112, respectively, when the members 110 and 114 are assembled and held together. Each of the struts 126 may include a pivot pin 127 about which the strut 126 pivots and a bearing 128 to rotatably support the pin 127.

[0079] The element 126 may comprise a ferromagnetic locking element or strut movable between first and second positions. The first position (shown in Figures 8 and 13) is characterized by abutting engagement of the locking element 126 with a load-bearing shoulder of a notch 113 of the member 110 and the shoulder of the pocket 124 formed in an end wall of the second member

114. The second position (solid lines in Figures 6 and 7) is characterized by non-abutting engagement of the locking element 126 with a load-bearing shoulder of at least one of the members 110 and 114. A biasing member or spring 129 (Figure 8) may be positioned under each of the struts 126 to urge its strut 126 to a return position which corresponds to the uncoupling position of the strut 126.

[0080] The electromagnetic system also includes a stationary electromagnetic source, generally indicated at 131, including at least one excitation coil 133 which is at least partially surrounded by an annular ring housing part 135. The housing part 135 includes first and second pieces 136 and 138 which are secured together. The coil 133 is held within a bobbin 134. When the coil 133 is energized (supplied with current), an axial symmetric, generally circular magnetic field loops out of the housing part 135 at a north pole of the housing part .135, through a magnetic insert or pole piece 137, into a first portion of the strut 126, out a second portion of the strut 126, through another insert or pole piece 139 and back into the housing pari 135 at a south pole of the housing part 135.

[0081] As shown in Figures 1 1 and 13, the pole pieces 137 and 139 may be segmented and secured to the third face 122 of the pocket plate 114 by screws 142. The pole pieces 137 and 139 are received and retained within the first and second passages 125 and 123, respectively, and arc in close-spaced opposition with the north and south poles, respectively, of the housing part 135.

[0082] The electromagnetic source 131, the element 126, the inserts 137 and 139, the air gaps between the inserts 137 and 139 and the element 126 and the air gaps between the source 131 and the inserts 137 and 139 make up a closed loop path containing magnetic flux so that the element 126 moves between its coupling and uncoupling positions when the coil 133 is supplied with current. The pole pieces 137 and 139 direct the magnetic field into the strut 126 to attract (or repel) the strut 126 and move the strut 126 into an engaged (or disengaged) position.

[0083] The above-noted electromagnetic systems reduce the frictional losses that are generally present in prior art actuation systems that act on locking elements within a rotating clutch member. This is made possible because the actuation system has no moving parts and it has no physical contact with the clutch member. Reducing the frictional losses provides a way to reduce the power consumption requirements of the actuation system.

[0084] In summary, the above-described clutch actuation system uses a stationary electromagnetic coil to produce a magnetic field that interacts with locking elements while they are moving with its rotating clutch member. The coil site inside a core/housing which is axially symmetric with a generally C-shaped cross section. The coil produces an axially symmetric magnetic field that loops out of one side of the C-shaped core and into the other side (like a horseshoe magnet revolved about an axis). The open end of the housing/core faces axially toward a non-magnetic clutch member that houses the locking elements and is free to rotate independently of the coil. The clutch member includes magnetic pole pieces that provide a low reluctance path for the magnetic flux from the coil to reach the locking element. At each controllable locking element, there is an individual magnetic circuit which takes the flux from a portion of the bulk field from the main core and directs it through one pole piece, through the locking element, and through the other pole piece to return back to the main core. The bulk field source is axially symmetric so that the individual magnetic circuits have a constant MMF (i,e. magnetomotive force) source regardless of their orientation relative to the main core; that is what enables the stationary coil to actuate locking elements in a rotating clutch member.

[0085] Obviously, the main core or coil housing may have a different shaped cross-section besides a generally C-shape.

[0086] Also, the flux path in the individual magnetic circuit components may be such that the flux lines that cross the air gaps between the main core and the pole pieces are oriented in the radial direction to reduce attractive forces between the main core and the clutch member.

[0087] Also, a lever may be coupled (not shown) to the stmt so that the magnetic force pulls on the lever to control the stmt instead of pulling on the stmt directly as shown herein. This action could engage or disengage the stmt.

[0088] While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention, Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form farther embodiments of the invention.