Diecast coupling member for use in an engageable coupling assembly

A diecast pocket plate or member having a sacrificial surface layer or portion is provided. The member is formed as a unitary die-casting from a die-casting alloy strengthened by an alloying material in a die-casting process. The diecast member includes a coupling face having a pocket which is sized and shaped to receive and nominally retain a locking member that moves in the pocket during an overrun condition of an engageable coupling assembly. The diecast member also includes a relatively hard base portion including particles of the strengthening alloying material of the die-casting alloy. The diecast member further includes a plurality of surface portions which define the pocket. At least one generally vertical surface portion of the surface portions is soft relative to the hard base portion and is substantially devoid of the particles of the alloying material so that the at least one generally vertical surface portion wears or deforms (i.e., is sacrificial) during contact of the locking member against the at least one generally vertical surface portion during the overrun condition.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to diecast coupling members such as pocket plates for use in engageable coupling assemblies such as one-way clutch assemblies.

2. Background Art

Pocket plates or members for use in one-way ratcheting type coupling or clutch assemblies are typically formed using powdered ferrous metals. In contrast to other metal-forming techniques, powdered metal parts are shaped directly from powder, whereas castings originate from molten metal.

Other methods of forming pocket plates have been tried in an attempt to reduce cost. For example, U.S. Pat. No. 6,333,112 discloses a laminated pocket plate. U.S. Patent Publication No. 2008/0135369 discloses a stamped clutch pocket plate. U.S. Pat. No. 6,125,980 discloses a pocket plate integrated within a hub such as by casting or molding to form an integral assembly. The hub comprises an aluminum alloy casting or a phenolic molding. The pocket plate itself is preferably a powdered metal part.

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.

SUMMARY

An object of at least one embodiment of the present invention is to provide a diecast coupling member for use in an engageable coupling assembly wherein the member has at least one generally vertical sacrificial surface portion.

In carrying out the above object and other objects of at least one embodiment of the present invention, a coupling member for an engageable coupling assembly is provided. The coupling member is formed as a unitary die-casting from a die-casting alloy strengthened by an alloying material in a die casting process. The coupling member includes a coupling face having a pocket which is sized and shaped to receive and nominally retain a locking member that moves in the pocket during an overrun condition of the assembly. The coupling member also includes a relatively hard base portion including particles of the strengthening alloying material of the die-casting alloy. The coupling member further includes a plurality of surface portions which define the pocket. At least one generally vertical surface portion of the surface portions is soft relative to the hard base portion and is substantially devoid of the particles of the alloying material so that the at least one generally vertical surface portion wears or deforms during contact of the locking member against the at least one generally vertical surface portion during the overrun condition.

The strengthening alloying material may include at least one of elemental Si, Cu, Mg, Ni and Zn.

The at least one generally vertical surface portion may include at least one of an outboard edge surface, an inside corner surface, a head edge surface and an inboard edge surface.

The wear may be at least one of abrasive-type wear and polishing-type wear.

The die casting alloy may be a non-ferrous alloy.

The coupling member may be a pocket plate.

The locking member may be a locking strut.

The coupling face may be an annular coupling face.

The coupling face may have a plurality of pockets. Each of the pockets may be sized and shaped to receive and nominally retain a corresponding locking member.

The coupling member may be a clutch member.

The pocket may have a T-shape and the pocket may have an inner recess for receiving a biasing spring such that the pocket is a spring pocket.

The annular coupling face may be oriented to face axially along a rotational axis of the assembly or the annular coupling face may be oriented to face radially with respect to the rotational axis.

Further in carrying out the above object and other objects of the at least one embodiment of the present invention, a pocket plate for a one-way clutch assembly is provided. The pocket plate is formed as a unitary die-casting from a die-casting alloy strengthened by an alloying material in a die casting process. The pocket plate includes an annular coupling face having a pocket which is sized and shaped to receive and nominally retain a locking strut that moves in the pocket during an overrun condition of the assembly. The plate also includes a relatively hard base portion including particles of strengthening alloying material of the die-casting alloy. The plate further includes a plurality of surface portions which define the pocket. At least one generally vertical surface portion of the surface portions is soft relative to the hard base portion and is substantially devoid of the particles of the alloying material so that the at least one generally vertical surface portion wears or deforms during contact of the locking strut against the at least one generally vertical surface portion during the overrun condition.

The coupling face may have a plurality of pockets. Each of the pockets may be sized and shaped to receive and nominally retain a corresponding locking strut.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS(S)

FIG. 1ais a perspective, photorealistic view of an overrunning pocket plate or member, generally indicated at10, of a one-way clutch or coupling assembly (not shown) constructed in accordance with at least one embodiment of the present invention.FIG. 1bis an enlarged perspective photorealistic view, partially broken away, taken within the circle labeled1binFIG. 1a. The plate10includes a plurality of pockets or recesses, generally indicated at12, circumferentially spaced about a rotary axis14or centerline of rotation (FIGS. 3 and 5b) within a radially extending face or surface16of the pocket plate10. The pockets12are sized and shaped to permit them to be die cast in a liquid metal, permanent mold, die-casting process. The plate10has an inner axially extending surface18at a pocket plate inner diameter (FIG. 3) on which splines20are formed for driving engagement with a rotating member (not shown). The plate10also has an outer axially extending surface22on which splines24are formed.

Each of the recesses or pockets12is T-shaped and is partially defined by an outboard edge surface26, an inside corner surface28, a head edge surface30, an inboard edge surface32and an inner recess34.

The one-piece pocket plate10is preferably formed as a unitary die casting from a non-ferrous casting alloy such as an aluminum silicon (Al—Si) die-casting alloy. The aluminum is strengthened by silicon and may also be strengthened by one or more of the following alloying elements: Cu, Mg, Ni and Zn. For example, the material may be an aluminum alloy 380 or 390 casting material. However, it is to be understood that other non-ferrous die-casting alloys may be used in forming the pocket plate10in a die-casting process.

FIG. 2is a metallographic sectional view of an outer surface portion of the cast pocket plate10to illustrate the casting microstructure of the solid casted plate10. During the liquid metal die-casting solidification process for the non-ferrous aluminum silicon alloy, an outer surface, relatively “soft skin” layer40, forms on a relatively hard base or substrate portion42of the pocket plate10. The layer40, consequently, forms or defines the surfaces26,28,30and32of the pockets12, as well as the surfaces18,22and16of the pocket plate10. The composite of the base or substrate layer material42has very hard (i.e. Rockwell hardness>60) particles44of silicon embedded therein. This is to be contrasted with the layer40which is free of primary silicon particles such as the particles44. In other words, the layer40is a substantially silicon-depleted surface layer40.

FIG. 3includes a schematic perspective view of a strut or pawl, generally indicated at48, together with a sectional view of the strut48received and nominally retained within one of the pockets12of the pocket plate10. Each of the struts48is generally of the type shown in U.S. Pat. No. 6,065,576 to mechanically couple the pocket plate10to a notch plate or member (not shown) when the plates attempt to rotate relative to each other in a direction opposite an overrun direction illustrated inFIG. 4ain which the two plates are allowed to overrun relative to each other.

As illustrated in the schematic perspective view inFIG. 3, each strut48includes first and second end surfaces,50and52, respectively, and a pair of oppositely projecting ears54which extend laterally from the strut48proximate from to its first end surface50. The ears54cooperatively engage its respective pocket's complementary inner surfaces including the surfaces28and30to thereby nominally position a first end of the strut48including the first end surface50in its respective pocket12.

Each of the locking formations or notches of the notch plate (not shown) is adapted to receive the free end portion of the strut48including the second end surface52of the strut48when the strut's free end is urged into a notch, for example, by a spring56seated beneath each strut48in its inner recess34of its pocket12.

Each of the strut end surfaces50and52preferably include substantially planar sections which are canted to a nominal angle relative to an upper face58of the strut48. The planar sections are substantially parallel to one another. Also, each of the ears54has a ramped upper surface60to prevent interference with the notch plate. Finally, each of the struts48includes spaced apart side surfaces62.

The sectional view ofFIG. 3provides a dynamic engagement analysis of a strut48within its respective pocket12wherein various forces acting upon the strut48are illustrated and described as follows:FR=Resultant Strut Force. The force available to push the strut48out of its pocket12(i.e. resultant force on the strut48).FS=Spring Force. The force created by the spring56used to push the strut48out of its pocket12for engagement with the notch plate (not shown).FC=Centrifugal Force. The effective weight of the strut48due to rotation of the pocket plate10during operation. (Force of strut48against pocket plate wall26.)FF=Friction Force. This force is created by the effective weight of the strut48(centrifugal force) acting on the pocket plate10. The higher the rotational speed the larger the friction force. This force prevents the strut48from pushing out of its pocket12.FP=Strut Pushout Force. The angle of the pocket plate wall26causes the strut48to push out of the pocket plate10. This is due to the centrifugal forces created by the rotation of the pocket plate10.FL=Fluid Force. This force is created by the effect of the strut48displacing transmission fluid when engaging into the notch plate. From empirical data, this force has been shown to have a minimal effect and is ignored.

The pocket plate (i.e. PP)10and associated strut48ofFIG. 3has particular utility in the following applications:PP has high % of continuous over-run and the NP (i.e., notch plate) is grounded (i.e., stationary);PP is stationary (i.e., 0 RPM) after lock-up; andPP RPM typically varies from 0 to 7000 RPM.

FIG. 4ais a perspective photorealistic view, partially broken away, illustrating an overrun direction of the pocket plate10and the resulting centrifugal force operating on the spring-biased strut48.

FIG. 4bis an enlarged perspective photorealistic view, partially broken away, of a pocket12with captions superimposed thereon to indicate that the vertical outboard edge surface26initially has a small draft due to cast tooling requirements. Also, the surface26is indicated as being worn by an edge of the side edge surface62of the strut48.

FIG. 5ais a view of the pocket plate10similar to the view ofFIG. 4b.

FIG. 5bis a side schematic view taken along lines5b-5bofFIG. 5aand illustrating the pocket12of the pocket plate10wherein the wall or surface26of the pocket12has an angle (i.e. θ inFIG. 3). The relatively soft surface layer40of the wall or surface26is effectively machined or abrasively worn due to the up-down motion of the relatively hard strut48within the pocket12during overrun. The strut48moves to the left as indicated by the arrow inFIG. 5bunder the centrifugal force to its dashed position wherein a lower edge of one of the side surface62of the strut48creates a substantially vertical surface out of the previously angled surface26. In other words, the small amount of draft on the pocket wall or surface26is reduced and becomes more vertical with a “step” below the vertical surface26. The resulting vertical surface26ensures that the strut48remains stable and is retained in its pocket12during overrun conditions. The abrasive wear or machining continues on the sacrificial layer40until the lower edge of the side surface62of the strut48encounters the harder substrate material in the base layer42.

FIG. 6is yet another photorealistic view, partially broken away, illustrating: a tooth reaction load on the splines20of the pocket plate10; applied load on the end surface52of the strut48; and a high compressive stress area of the pocket plate10caused by the second end surface50of the strut48in response to the load applied on the first end surface52when the strut48is performing its locking function with respect to a notch plate. The compressive stress area or head edge30of the pocket12also experiences polishing type wear due to the up-down motion of the strut48. Further, the inboard edge or surface32experiences less severe wear.

FIG. 7ais a view similar to the view ofFIGS. 4band5aafter the strut48has worn the various sacrificial layers defining surfaces26,28,30and32of the pocket12.FIG. 7bis an electron microscopic image which includes the surfaces26and28ofFIG. 7a. Abrasive wear in each of the surfaces26and28is evident.FIG. 7cis an enlarged view indicated by the notation “7c” inFIG. 7bwherein wear and a step of apparent deformed metal are shown at the surface28.FIG. 7dis an enlarged view indicated by the notation “7d” inFIG. 7bwherein wear and a step of apparent deformed metal are shown at the surface26. Again, the wear and deformation are caused by the up and down motion of the strut48when the plate10is rotating, thereby causing the strut48to move laterally against the surface26by centrifugal force.