Rotary power transmission device

Abstract

The utility model relates to a rotary power transmission device. Specifically, in at least some embodiments, a rotary power transfer device includes: a device housing having an interior in which a plurality of gears are received for rotation; a clutch received within the device housing and having a clutch ring selectively engageable with one of the plurality of gears; and an actuator having a coil and a plunger driven for movement along the axis and relative to the clutch ring. The plunger has a first position and a second position in which the clutch ring is engaged with the one of the plurality of gears. The plunger includes a first body formed at least partially from a magnetically responsive material, and the first body includes a radially outer surface, a radially inner surface, and a front face that is axially variable and arranged such that the radially outer portion of the front face is axially forward of the radially inner portion of the front face.

Description

Technical Field

[0001] This disclosure generally relates to an electromagnetic actuator for a drivetrain system (as a non-limiting example, such as a clutch, differential, and wheel-axle disconnect assembly). Background Technology

[0002] Electromagnetic actuators can be used to linearly actuate devices such as clutches. However, the space allocated to the actuator is small, and achieving the required response time and force is difficult without significantly increasing the size and weight of the components (which is undesirable). Utility Model Content

[0003] In at least some embodiments, a rotary power transmission device includes: a housing having an interior in which a plurality of gears are received for rotation; a clutch received within the housing and having a clutch ring selectively engaging with one of the plurality of gears; and an actuator having a coil and a plunger driven to move along an axis and relative to the clutch ring. The plunger has a first position in which the clutch ring is not engaged with the one of the plurality of gears, and a second position in which the clutch ring is engaged with the one of the plurality of gears. The plunger includes a first body formed at least partially of a magnetically responsive first material and a second body formed at least partially of a second material, wherein the first body includes a radially outer surface, a radially inner surface, and a front face, the front face being axially variable and arranged such that a radially outer portion of the front face is axially ahead of a radially inner portion of the front face.

[0004] In at least some embodiments, the device housing includes an axially extending surface radially disposed between the coil and a radially outer surface, and axially overlapping at least a portion of the radially outer surface at all locations of the plunger. In at least some embodiments, the front of the first body includes a nose portion extending from a transition portion axially spaced from the front, and wherein the radially outer surface slopes toward a radially inner surface in the nose portion such that the radial dimension of the first body decreases from the transition portion to the front, and wherein the gap between the radially outer surface and the axially extending surface decreases as the plunger moves toward a second position.

[0005] In at least some embodiments, the front of the first body includes a nose portion that extends from a transition portion axially spaced from the front, and wherein a radially outer surface in the nose portion is inclined toward a radially inner surface such that the radial dimension of the first body decreases from the transition portion to the front.

[0006] In at least some embodiments, the device housing includes a recess defined by an end wall, wherein the front of the first body is received in the recess when the plunger is in a second position. In at least some embodiments, the end wall has a radially inner surface and a radially outer surface that is axially offset from the radially inner surface. In at least some embodiments, the end wall defines a portion of a circumferentially extending recess in the device housing. In at least some embodiments, the device housing includes an annular surface, and the plunger includes a radially inner surface adjacent to the annular surface, sliding along the annular surface when the plunger moves to a first position and a second position and moves between the first and second positions, wherein the recess is radially offset from the annular surface.

[0007] In at least some embodiments, the second body includes an axially extending foot having an axial end arranged to engage a clutch ring, and a nose portion being axially spaced from the axial end of the foot such that the nose portion does not engage the clutch ring.

[0008] In at least some embodiments, the nose portion tapers radially at an angle between 0.5 degrees and 30 degrees. In at least some embodiments, the front is axially inclined relative to the radius of the radially outermost portion extending to the front at an angle between 0.1 degrees and 45 degrees.

[0009] In at least some embodiments, a rotary power transmission device includes a housing, a clutch, and an actuator. The housing has an interior in which a plurality of gears are received for rotation, an annular surface, and axially extending surfaces arranged radially spaced from the annular surface. The clutch is received within the housing and has a clutch ring capable of selectively engaging one of the plurality of gears. The actuator has a coil and a plunger driven for movement along the annular surface and has an axis. The plunger is driven relative to the clutch ring and has a first position in which the clutch ring is not engaged with the one of the plurality of gears, and a second position in which the clutch ring is engaged with the one of the plurality of gears. The plunger includes a first body formed at least partially of a magnetically responsive first material and a second body coupled to the first body and slidable along the annular surface. The first body includes a radially outer surface, a radially inner surface, and a front end, the front end being axially variable and arranged such that a radially outer portion of the front end is axially ahead of a radially inner portion of the front end, and an axially extending surface axially overlaps at least a portion of the radially outer surface of the plunger at at least some locations on the plunger.

[0010] Various features and components may be combined together unless they are mutually exclusive according to the following description, which is intended to illustrate the various features and not to limit the utility model described herein. Attached Figure Description

[0011] The following detailed description and best mode of preferred embodiments will be explained with reference to the accompanying drawings, in which:

[0012] Figure 1 This is a schematic diagram of the vehicle's powertrain components;

[0013] Figure 2 This is a cross-sectional view of a differential with an electrically actuated locking mechanism, wherein the differential is shown in the open position;

[0014] Figure 3 This is a partial view of a portion of the differential, including the plungers;

[0015] Figure 4 This is an enlarged partial view of a portion of the differential's plunger and housing;

[0016] Figure 5 , Figure 6 and Figure 7 The plunger is shown in the first position, the intermediate position, and the second position;

[0017] Figure 8 The corresponding portions of the plunger and differential housing of the first body with alternative shapes are shown;

[0018] Figure 9 The corresponding portions of the plunger and differential housing of the first body with alternative shapes are shown;

[0019] Figure 10 This is an end view of the plunger; and

[0020] Figure 11 This is a side cross-sectional view of the plunger. Detailed Implementation

[0021] For more detailed information, please refer to the diagram. Figure 1A vehicle drivetrain 12 is shown, which supplies power from an engine 14 to multiple wheels, including front wheels 15 and rear wheels 16. The engine 14 supplies torque via a transmission 17 and a power transmission unit 18 providing an output shaft 20. The output shaft 20 is coupled to a first driveshaft 21, which is coupled to a rear drive unit 22, which may include a differential assembly 23. The power transmission unit 18 or other device may have an output shaft 24 coupled to a front drive unit 25 (which may include a differential assembly 26) via a second driveshaft 27. A left front axle 28 and a right front axle 29 are coupled to the drive unit 25 / differential 26, allowing relative rotation between the axles 28, 29 and the front wheels 15. A left rear axle 30 and a right rear axle 32 are coupled to the rear drive unit 22 / differential 23, allowing relative rotation between the axles 30, 32 and the rear wheels 16. The power transmission unit 18 may include a disconnect component that, when in the connected state, transmits torque to the second driveshaft 27 to drive the front wheels 15. When connected or disconnected, the power transmission unit 18 may provide torque to the first driveshaft 21 to drive the rear wheels 16. Thus, depending on the state of the disconnection device, the drivetrain 12 may provide torque to either the rear wheels 16 only or to all four wheels 15, 16.

[0022] Of course, other drivetrain configurations can be used as desired. For example, although shown in a rear-wheel-drive-based drivetrain, a locking differential can also be used in all-wheel-drive systems based on the front wheels, or even in two-wheel-drive engine / front-wheel-drive or engine / rear-wheel-drive drivetrains, and in electric axle (e-axle) (the final drive unit driven by an electric motor). This disclosure is not limited to drivetrain configurations, and the devices described herein can be used in a wide range of components such as clutches, axle / shaft disconnect assemblies, differentials, etc.

[0023] Now for reference Figure 2 The first rear axle 30 is connected to the first side gear 34 within the differential 23. Similarly, the second rear axle 32 is connected to the second side gear 36 within the differential 23. The side gears 34 and 36 are housed within the housing 37 of the differential 23 (which may be referred to as the differential housing or device housing). The differential also includes pinions 38 and 40, which mesh with the side gears 34 and 36 respectively, and are mounted on the pinion shaft 42 within the housing 37.

[0024] For selective locking and unlocking of differential 23, a clutch assembly 46 is provided. Clutch assembly 46 may have an actuated state and a disengaged state, and in one state, the clutch assembly engages one of the side shafts (e.g., 32) to differential housing 37, causing the engaged side shaft to rotate with the housing. This, in turn, causes the other side shaft 30 to rotate in unison with housing 37 and the side shaft 32 engaged with housing, such that both side shafts 30, 32 rotate at the same speed.

[0025] In at least some embodiments, the clutch assembly 46 is electrically actuated and includes an actuator having a solenoid 48 with an annular coil 49 and a drive component that may include an armature or plunger 54 at least partially radially inward of the coil and axially overlapping the coil. Figure 2 , Figure 3 , Figure 10 and Figure 11 In at least some embodiments, the plunger 54 is also annular, the plunger and coil 49 are arranged coaxially and carried by housing 37 for rotation with the housing, and a side shaft (here, a second side shaft 32) extends coaxially through a portion of housing 37, which extends through the coil and plunger. Electrical power is supplied to coil 49 via power line 50 to generate a magnetic field that moves plunger 54 relative to the coil and differential housing 37 from a first or retracted position to a second or forward position. As explained below, when power is not supplied to coil 49, a biasing member such as spring 55 may act on plunger 54 or on a member engaging with plunger to facilitate the return of plunger 54 from the second position to the first position. In at least some embodiments, clutch assembly 46 is actuated when plunger 54 is in the second position and disengaged when plunger is in the first position. Although in the example shown, the plunger 54 is in its second position when power is supplied to the coil 49 and moves to its first position when power is not supplied to the coil, the opposite could be desired (e.g., the clutch assembly 46 could be moved to the actuated position by the biasing member 55 and disengaged by supplying power to the coil).

[0026] In at least some embodiments, as described below, the clutch assembly 46 may further include or be associated with a clutch element, referred herein as a clutch ring 56, which is adapted to be driven by a plunger 54 and engage with a side gear 34. The clutch ring 56 may be annular, and a portion of the second side gear 36 and / or shaft 32 may extend through the clutch ring. The clutch ring 56 may include a rear end 57 engageable by the plunger 54 and a front end 59 having at least one engagement feature 58, such as a gear or clutch tooth 58 (e.g., a claw-shaped clutch tooth), configured to engage a corresponding engagement feature 60 (e.g., a gear or claw-shaped clutch tooth) formed on the rear end of the first side gear 34. As described above, a spring 55 may act on the clutch ring 56 to push the clutch ring into the plunger 54 and move the plunger to its first position when no power is supplied to the coil 49. In the illustrated embodiment, the plunger 54 is located on one side adjacent to the housing wall 62, and the clutch ring 56 is located on the other side adjacent to the wall 62. Wall 62 includes an orifice 64, and plunger 54 and clutch ring 56 each include axially extending feet 66 and 68 that extend into or through the orifice 64 in the wall, such that the plunger and clutch ring engage with each other across or through the wall. Like coil 49 and plunger 54, clutch ring 56 is also carried by housing 37 and rotates with housing 37.

[0027] Figure 2 The differential 23 shown is depicted in the open mode or position. In the illustrated embodiment, in the open position of the differential, no power is supplied to the coil 49, the plunger 54 is in its first position, and the clutch ring 56 is not engaged with the side gear 34, allowing the side gear to rotate relative to the clutch ring 56 and the housing 37. In the open position, the side shafts 30 and 32 can rotate at different speeds. However, certain driving conditions may make it desirable for the side shafts 30 and 32 to rotate in unison, so that torque is applied to both wheels.

[0028] In the locked position, power is supplied to coil 49, and plunger 54 advances to its second position, which drives clutch ring 56 to engage with side gear 34 (i.e., teeth 58 and 60 engage and mesh). Therefore, side gear 34 is coupled to housing 37 such that it rotates with housing but not relative to housing. In effect, second side shaft 32 is locked to housing 37 and rotates with housing 37, which in turn forces first side shaft 30 and second side shaft 32 to rotate in unison. Although shown in relation to a locking differential, the clutch and actuator arrangement described herein can be used as desired in other devices where linear actuators may be useful, including those with friction clutches and disengagement components, as well as in internal combustion engine powertrains, electric powertrains, and hybrid powertrains.

[0029] like Figure 2-4As shown in Figures 8-11, plunger 54 may be formed of a variety of materials, including materials that are magnetically responsive to the magnetic field generated by coil 49, and at least one other material that may or may not be responsive to the magnetic field. Thus, when the magnetic field is generated by coil 49, plunger 54 can be driven from one position to another (e.g., from a retracted position to an advanced position). As used herein, a material responds to the magnetic field if the magnitude of the magnetic field generated by solenoid 48 of the type used in the application (such as those described herein) is sufficient to cause movement of a component formed of or comprising that material.

[0030] In at least some implementations, such as Figure 2 , Figure 3 and Figure 11 As shown, plunger 54 includes a central axis 73 ( Figure 2 and 11 The body (shown in the diagram) is defined by a first body 74 and a second body 76 that are joined together and move as a unit or component and do not separate during use. The first body 74 may be formed of a magnetically responsive material and may be received adjacent to and radially inward of the coil 49, with a small air gap between them. The second body 76 may have at least a portion radially inward of at least a portion of the first body 74. The second body 76 may be annular and may radially overlap a portion of the first body 74 in at least some embodiments. The second body 76 may be readily overmolded onto the first body 74 to facilitate the formation of the second body and the connection of the first and second bodies together; however, other forming processes such as, but not limited to, casting, stamping, or extrusion may be used. The second body 76 may define part or all of the foot 66 of the plunger 54, which may extend axially beyond the first body 74 to the axial end of the foot 66 arranged to engage the clutch ring 56. The second body 76 may be formed of a non-magnetically responsive material (e.g., plastic, aluminum, stainless steel, etc.) and may provide various magnetic flux shieldings to improve the magnetic field strength in or within the region of the first body 74, ensuring proper response of the plunger 54 when the coil 49 is energized. In this way, the magnetic field is more concentrated or stronger in the region of the first body 74, increasing the magnetic flux at or within the first body and improving the response of the plunger 54 to the generated magnetic field.

[0031] like Figure 3 As shown, the second body 76 may have a radially inner surface 78 that receives adjacent to or around the annular surface 79 of the differential housing 37. The inner surface 78 may define a pilot diameter for receiving the plunger 54 on the annular surface 79 of the differential housing 37 to guide axial sliding movement of the plunger relative to the differential housing.

[0032] like Figure 4As shown, the first body 74 has a radially inner surface 80 adjacent to the radially outer surface 82 of the second body 76, and a radially inner surface 86 that is closest to the coil 49 of the plunger 54. Figure 3 The radial outer surface 84 of the part, the front end 88 located closer to the first axial end of the clutch ring 56, and the rear end 90 located at the second axial end opposite to the first end. Figure 3 The front end 88 may define the axial end of the plunger 54 in a circumferentially extending region between the feet 66 of the second body 76. The outer surface 84 of the first body 74 is the portion of the plunger 54 closest to the radially inner surface 86 of the coil 49. The outer surface 84 is also adjacent to an axially extending surface 92 of the differential housing 37. In at least some embodiments, the axially extending surface 92 is received between the coil 49 and a portion of the first body 74 and may axially overlap with a portion of the first body 74 including at least a portion of the front end 88. In this way, the axially extending surface 92 may be part of the flux path for the magnetic field generated by the coil 49 and act on the first body 74 to drive the first body 74 between a first position and a second position.

[0033] In at least some embodiments, the first body 74 includes a nose portion 94 that tapers to provide a reduced outer diameter from a transition 96 at the beginning of the nose portion 94 to the front end 88 (wherein, the diameter from the transition 96 to the rear end 90 may be constant if desired). The tapered outer surface 84 in the nose portion 94 provides an air gap 98 between the axially extending surface 92 of the housing 37 and the first body 74, which decreases as the first body 74 moves toward a second position in which the overlap between the first body 74 and the axially extending surface 92 is greater than in the first position. Figure 5 , Figure 6 and Figure 7 This is illustrated by way of a non-limiting example, where the plunger is shown in the first position ( Figure 5 ), middle position ( Figure 6 ) and in the second position ( Figure 7 As the plunger moves from the first position to the second position, the clearance decreases radially. In this way, as the plunger 54 advances toward the clutch ring 56, the force provided by the magnetic field on the first body 74 increases to facilitate the movement of the plunger 54 and the clutch ring 56, increase the rate of movement to improve the response time of the device, and provide greater force when the plunger engages and drives the clutch ring 56.

[0034] Refer again Figure 4The front face 88 of the first body 74 may be axially inclined such that the outermost radial portion of the front face 88 is axially ahead of the innermost radial portion of the front face. In at least some embodiments, the outer radial portion 100 of the front face 88 is axially ahead of the inner radial portion 102 of the front face 88, wherein: 1) the outer portion 100 includes a transition or joint 104 between the outer surface 84 and the front face 88 and extends toward a radial midpoint 106 between the outer surface 84 and the inner surface 80; and 2) the inner portion 102 extends between the inner surfaces 80 and extends to the midpoint 106. Although the first body 74 is shown having a front face 88 that is linear from the outer surface 84 along most of the distance between the outer surface 84 and the inner surface 80 (e.g., from the outer surface 84 and beyond the midpoint 106), the front face 88 may be stepped (e.g., ...). Figure 8 (as shown in the general diagram), it can be curved (such as...) Figure 9 Generally shown), or otherwise arranged, the upper portion of the front is axially offset and in front of the lower portion of the front (wherein, "in front" indicates the direction of movement of the plunger 54 and / or closer to the clutch ring). Furthermore, in the example shown, the inner portion 102 of the front 88 includes a chamfered or beveled surface 108 extending from the inner surface 80 to a transition 110 located between the inner surface 80 and the midpoint 106, and arranged at an angle different from the rest of the front 88. This beveled surface 108 facilitates the assembly of the plunger 54 and provides clearance to the rear side of the foot of the plunger foot 66.

[0035] Therefore, the outer portion 100 of the front 88 overlaps more axially than the inner portion 102 by the axially extending surface 92. In this way, the size of the air gap 98 at the first position of the plunger 54 can be smaller than if the front 88 were not axially tilted, and this can provide a higher initial magnetic force to the plunger 54 when the coil 49 is energized, while still providing a reduced air gap 98 when the plunger 54 is driven forward to move the clutch ring 56, and thus providing an increased force on the plunger 54.

[0036] In at least some embodiments, the outer surface 84 of the first body 74 tapers radially in the nose portion 94 at an angle between zero or 0.5 degrees and 30 degrees, and the front end 88 is inclined at an angle between 0.1 degrees and 45 degrees relative to a radius (such as the radius extending to the outermost radial portion of the front end). In at least some embodiments, the first body 74 has a radial thickness between 1 mm and 10 mm, and the portion of the front end 88 between the midpoint 106 and the outer surface 84 is axially forward of the front end 88 at the transition portion 110. Furthermore, when the stroke length of the plunger 54 is between 1 mm and 8 mm, the air gap 98 can be between 0.2 mm and 3 mm in the first position of the plunger 54, and between 0.05 mm and 2 mm in the second position of the plunger 54. In at least some embodiments, the angle 112 of the front end 88 is greater than or equal to the taper angle 114 of the outer surface 84 in the nose portion 94 of the first body 74.

[0037] like Figure 3 and Figure 4 As shown, the differential housing 37 may include a recess 116 into which the front surface 88 of the first body 74 is received when the plunger 54 is in the second position. The recess 116 is defined by a groove extending circumferentially between adjacent orifices 64, radially aligned with the first body 74 of the plunger 54, and partially defined by an end wall 118 whose shape and position are configured to allow for a full range of movement of the plunger 54. The end wall 118 has a radially outer surface 120 that is axially inclined or offset from a radially inner surface 122 and may be at the same or different angle 124 as, or have the same or different shape as, the front surface 88 of the first body 74 of the plunger 54. The recess 116 allows the plunger 54 to move undisturbed through a longer stroke to achieve sufficient travel length for reliable engagement and disengagement of the clutch.

[0038] In commercial applications, the size of the actuator 48 and the differential is severely limited, and it may be difficult to utilize sufficient force from the coil 49 to provide a suitable actuation stroke for the plunger. The forward-sloping front end 88 of the plunger first body 74 enables a higher initial actuation force compared to a body with a radially extending front end (e.g., a front end that is not sloping radially, with one portion axially ahead of the other), where at least a portion of the front end 88 overlaps with or is within a smaller gap from the adjacent surface 92 of the housing 37. Furthermore, the tapered nose portion 94 of the first body allows for a reduced clearance 98 between the first body 74 and the differential housing 37 to provide increased actuation force along the stroke length of the plunger 54, thus providing greater force during the portion of the stroke in which the plunger 54 engages and moves the clutch ring 56 (or other components driven by the plunger 54).

[0039] Furthermore, the recess 116 in the differential housing can be provided to be radially offset and spaced from the surface 79 along which the plunger 54 moves, along which the wall or structure of the side shaft can be partially received and adjacent to the side gear connected to the side shaft. This region of the differential housing 37 is subjected to higher loads during use, and a recess in this region would be undesirable or would require an overall increase in wall thickness, which would increase the size and weight of the housing. Because the recess 116 is only required for the first body 74 and not for the second body 76, the recess is spaced from the region of the differential housing under higher loads during use, and the recess is confined to the region of the differential housing 37 subjected to lower forces, and this region can tolerate the reduction in material in the region of the recess. In this way, the differential housing 37 can be optimized, while enabling improvements in the performance of the actuator 48 and the plunger 54.

[0040] The forms of the present invention disclosed herein constitute the present preferred embodiments, and many other forms and embodiments are possible. It is not intended to refer to all possible equivalents or branches of the present invention. It is understood that the terminology used herein is descriptive only and not restrictive, and various changes may be made without departing from the spirit or scope of the present invention.

[0041] Unless expressly indicated otherwise herein, all terms used in the claims are intended to be given the widest reasonable composition and their ordinary meaning as understood by one skilled in the art. Specifically, unless the claims expressly state a limitation to the contrary, the use of singular articles such as “a,” “the,” and “the” should be understood to refer to one or more of the elements indicated.

Claims

1. A rotating power transmission device, characterized in that, The rotating power transmission device includes: The device housing has an interior in which multiple gears are received for rotation; A clutch, received within the device housing and having a clutch ring capable of selectively engaging one of the plurality of gears; and An actuator having a coil and a plunger driven to move along an axis and relative to the clutch ring, the plunger having a first position in which the clutch ring is not engaged with one of the plurality of gears, and the plunger having a second position in which the clutch ring is engaged with one of the plurality of gears, and the plunger comprising a first body formed at least partially of a magnetically responsive first material and a second body formed at least partially of a second material, wherein the first body comprises a radially outer surface, a radially inner surface and a front face, the front face being axially variable and arranged such that the radially outer portion of the front face is axially ahead of the radially inner portion of the front face.

2. The apparatus according to claim 1, wherein, The device housing includes an axially extending surface that is radially arranged between the coil and the radially outer surface, and axially overlaps with at least a portion of the radially outer surface at all locations of the plunger.

3. The apparatus according to claim 1, wherein, The front of the first body includes a nose portion extending from a transition portion axially spaced from the front, and wherein the radially outer surface of the nose portion is inclined toward the radially inner surface, such that the radial dimension of the first body decreases from the transition portion to the front.

4. The apparatus according to claim 2, wherein, The front of the first body includes a nose portion extending from a transition portion axially spaced from the front, and wherein the radially outer surface is inclined toward the radially inner surface in the nose portion such that the radial dimension of the first body decreases from the transition portion to the front, and wherein the gap between the radially outer surface and the axially extending surface decreases as the plunger moves toward the second position.

5. The apparatus according to claim 1, wherein, The device housing includes a recess defined by an end wall, and wherein the front of the first body is received in the recess when the plunger is in the second position.

6. The apparatus according to claim 5, wherein, The end wall has a radially inner surface and a radially outer surface that is axially offset from the radially inner surface.

7. The apparatus according to claim 5, wherein, The end wall is defined as part of a circumferentially extending groove in the device housing.

8. The apparatus according to claim 5, wherein, The device housing includes an annular surface, and the plunger includes a radially inner surface adjacent to the annular surface, and slides along the annular surface when the plunger moves to the first position and the second position and between the first position and the second position, wherein the recess is radially offset from the annular surface.

9. The apparatus according to claim 3, wherein, The second body includes an axially extending foot having an axial end arranged to engage the clutch ring, and a nose portion axially spaced from the axial end of the foot such that the nose portion does not engage the clutch ring.

10. The apparatus according to claim 4, wherein, The second body includes an axially extending foot having an axial end arranged to engage the clutch ring, and a nose portion axially spaced from the axial end of the foot such that the nose portion does not engage the clutch ring.

11. The apparatus according to claim 3 or 4, wherein, The nasal portion tapers radially at an angle between 0.5 degrees and 30 degrees.

12. The apparatus according to claim 1, wherein, The front end is axially inclined at an angle between 0.1 degrees and 45 degrees relative to the radius of the radially outermost portion extending to the front end.

13. The apparatus according to claim 11, wherein, The front end is axially inclined at an angle between 0.1 degrees and 45 degrees relative to the radius of the radially outermost portion extending to the front end.

14. The apparatus according to claim 1, wherein, The front end is axially inclined at an angle between 0.1 degrees and 45 degrees relative to the radius of the radially outermost portion extending to the front end.

15. A rotating power transmission device, characterized in that, The rotating power transmission device includes: The device housing has an interior in which a plurality of gears are received for rotation, and the device housing also has an annular surface and an axially extending surface arranged radially spaced apart from the annular surface; A clutch, received within the device housing and having a clutch ring capable of selectively engaging one of the plurality of gears; and An actuator having a coil and a plunger driven for movement along the annular surface and having an axis, the plunger being driven relative to the clutch ring and having a first position in which the clutch ring is not engaged with one of the plurality of gears, and a second position in which the clutch ring is engaged with one of the plurality of gears, the plunger comprising a first body formed at least partially of a magnetically responsive first material and a second body coupled to the first body and slidable along the annular surface, wherein the first body comprises a radially outer surface, a radially inner surface and a front face, the front face being axially variable and arranged such that a radially outer portion of the front face is axially ahead of a radially inner portion of the front face, and wherein the axially extending surface axially overlaps at least a portion of the radially outer surface of the plunger at at least some locations on the plunger.

16. The apparatus according to claim 15, wherein, The front of the first body includes a nose portion extending from a transition portion axially spaced from the front, and wherein the radially outer surface of the nose portion is inclined toward the radially inner surface, such that the radial dimension of the first body decreases from the transition portion to the front.

17. The apparatus according to claim 15, wherein, The device housing includes a recess defined by an end wall, and wherein the front of the first body is received in the recess when the plunger is in the second position.

18. The apparatus according to claim 17, wherein, The end wall has a radially inner surface and a radially outer surface that is axially offset from the radially inner surface.

19. The apparatus according to claim 17, wherein, The plunger includes a radially inner surface adjacent to the annular surface and slides along the annular surface when the plunger moves to the first position and the second position and between the first position and the second position, wherein the recess is radially offset from the annular surface.

20. The apparatus according to claim 16, wherein, The nasal portion tapers radially at an angle between 0.5 degrees and 30 degrees, and the front portion is axially inclined at an angle between 0.1 degrees and 45 degrees relative to the radius of the radially outermost portion extending to the front.

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