Patent Application
20150063999
The present invention relates to the field of stator assemblies, particularly the operative connection between the stator body and outer race, and more particularly to the functional attachment of the stator and the outer race.
Torque converters are used with automatic transmissions in motor vehicles to allow for transmission of torque from the engine to the transmission. Stator assemblies are used to direct fluid flow from the turbine to the pump in the torque converter to maintain rotation of the torque converter. Stator assemblies include a one-way clutch (clutch) that allows the stator to rotate with the pump and turbine at higher speed ratios and prevents stator rotation in the opposite direction at lower speed ratios including vehicle launch, for example.
The clutch includes an outer race that is functionally connected to the stator. By functionally attached is meant that a component or device is connected either directly or indirectly to a second component and causes that second component to function. For example, the outer race of the clutch contacts or is attached to the stator and allows the stator to rotate (freewheel) with the torque converter at high speed ratios and prevents stator rotation at lower speeds enabling the stator to redirect fluid flow to the torque converter pump.
Several difficulties must be overcome in the manufacture of a stator assembly. To reduce cost, stators are usually fabricated from softer metals, such as aluminum, while outer races are customarily constructed from harder materials, such as steel, to withstand the torque applied to the clutch. Because of the high fluid temperatures developed during operation of a torque converter, the stator and outer race will expand at different rates as each will have different coefficients of thermal expansion, with the aluminum of the stator expanding faster than the steel outer race. This can reduce the durability of the stator assembly as the functional attachment between the stator and outer race can be significantly altered.
Alternative designs use radial projections, or lugs, cast in the stator housing to drive slots in the outer race. In order to assemble the two components, some lash is present in the joint. Therefore, when the clutch locks, the rotating stator lug will collide against the stationary outer race slot. These collisions cause the harder outer race to eventually wear the softer stator lug.
Moreover, the design of stator assemblies usually necessitates the use of close tolerances between the stator and outer race to provide the most efficient operation. It is less expensive to machine smooth cylindrical surfaces on a lathe rather than mill surfaces with projections in the inner surface of the stator what would be used to form the functional attachment with the outer race.
U.S. Pat. No. 5,056,581 to Tarawa, et al., which patent is incorporated herein by reference in its entirety, discloses a method for forming a stator-outer ring (outer race) in which the outer race is forged to include projections distributed on the outer edge of the race. The stator is formed by molding or casting using the outer race as an insert. This method forms a close connection between the outer race and stator but requires expensive molding and forging processes. U.S. Pat. No. 8,197,202 to Olsen, et al., which patent is incorporated herein by reference in its entirety, discloses a stator housing with precast grooves to improve durability of a press-fit connection with the outer race, which has teeth or projections on the edge of the outer race that fit into the precast grooves. This connection can be altered by differences in thermal expansion.
Thus, it can be seen that there remains a need in the field to provide a stator assembly in which lash can be reduced or eliminated, the problems of different rates of thermal expansion can be overcome, and smooth surfaces can be used to manufacture the stator assembly.
The present invention broadly an outer race for a stator assembly comprising: a body; an outer circumferential edge; a plurality of keys extending radially outward from the outer circumferential edge, each of the plurality of keys having a thickness, a pair of opposing sides, and an outer key edge extending between each one of the pair of opposing sides; at least one spline projecting from at least one of the two opposing sides; and, an inner circumferential edge. In a preferred embodiment, a plurality of splines project transversely from both opposing sides of each key.
The present invention also broadly comprises a stator assembly comprising: a stator and an outer race. The stator includes: a stator body; an outer circumferential stator edge; an inner circumferential edge; an outer surface; and, an inner circumferential surface including a plurality of recesses; a plurality of blades distributed on the inner surface. The outer race, includes: a body; an outer circumferential edge; a plurality of keys extending radially outward from the outer circumferential edge, each of the plurality of keys having a thickness, a pair of opposing sides, and an outer edge extending between each one of the pair of sides; at least one spline projecting from at least one of the two opposing sides; and, an inner circumferential edge. Each of the at least one spline form grooves within respective stator recesses when the outer race is pressed into the stator body.
The invention also broadly comprises a method of fabricating a stator assembly wherein a stator includes: a stator body; an outer circumferential stator edge; an inner circumferential edge; an outer surface; and, a inner circumferential surface including a plurality of recesses; a plurality of blades distributed on the inner surface; and, wherein an outer race includes: a body; an outer circumferential edge; a plurality of keys extending radially outward from the outer circumferential edge, each of the plurality of keys having a thickness, a pair of opposing sides, and an outer edge extending between each one of the pair of sides; at least one spline projecting from at least one of the two opposing sides; and, an inner circumferential edge;
wherein each of the at least one spline forms grooves within respective stator recesses when the outer race is pressed into the stator body with the method comprises positioning each of the keys over the slots; and, pressing the keys into the stator slots in an axial direction. The plurality of splines form grooves within the stator slots when the outer race is pressed into the stator body.
One object of the invention is to supply a stator assembly that maintains efficient operation in a high heat environment.
A second object of the invention is to provide a stator-outer race connection in which lash is reduced or eliminated.
A third object of the invention is to present a stator assembly in which the parts are easily machined.
The nature and mode of the operation of the present invention will now be more fully described in the following detailed description of the invention taken with the accompanying drawing Figures, in which:
At the outset, it should be appreciated that like drawing numbers on different drawing views identify identical structural elements of the invention. It also should be appreciated that figure proportions and angles are not always to scale in order to clearly portray the attributes of the present invention.
While the present invention is described with respect to what is presently considered to be the preferred embodiments, it is understood that the invention is not limited to the disclosed embodiments. The present invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
Furthermore, it is understood that this invention is not limited to the particular methodology, materials and modifications described and as such may, of course, vary. It is also understood that the terminology used herein is for the purpose of describing particular aspects only, and is not intended to limit the scope of the present invention, which is limited only by the appended claims.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this invention belongs. It should be appreciated that the term “substantially” is synonymous with terms such as “nearly”, “very nearly”, “about”, “approximately”, “around”, “bordering on”, “close to”, “essentially”, “in the neighborhood of”, “in the vicinity of”, etc., and such terms may be used interchangeably as appearing in the specification and claims. It should be appreciated that the term “proximate” is synonymous with terms such as “nearby”, “close”, “adjacent”, “neighboring”, “immediate”, “adjoining”, etc., and such terms may be used interchangeably as appearing in the specification and claims. Although any methods, devices or materials similar or equivalent to those described herein can be used in the practice or testing of the invention, the preferred methods, devices, and materials are now described.
Outer race 100 also includes inner circumferential edge 118 (“edge 118”). In the embodiment shown, a plurality of interior struts 120 extend radially inward from edge 118. In the same embodiment, inclined ramps 122 extend part of the distance between the individual struts 120 along inner circumferential edge 118. Shoulder 124 indicates where the slope of ramp 122 ends.
Stator 200 has a thickness extending between the front side (not seen in
Struts 120 extend from inner circumferential edge 118 toward inner race 300. Rollers 126 are positioned between ramp 122 and outer inner race edge 304. Adjacent to each roller 126 is spring 128. Rollers 126 contact and roll on outer inner race edge 304. Inner race 300 includes inner race body 302. Teeth 308 extend radially inward from inner circumferential edge 306 of inner race 300.
In the freewheeling condition, outer race 100 and stator 200, connected by splines 117, rotate together in the direction of the arrow Put in arrow. Springs 128 push rollers 126 farther onto ramp 118 where there is a larger gap between inner edge 118 and outer edge 306 of inner race 300. This allows outer race 100 and stator 200 to rotate freely. In the locked condition, stator 200 and outer race 100 rotate in the opposite direction forcing roller 126 to be wedged between inner edge 118 and outer edge 306 of inner race 300. This prevents stator 200 from rotating enabling it to reverse the fluid flow exiting the turbine and entering the pump of the torque converter.
Keys 116 will include at least one spline 117 projecting form at least one side 116b. Preferably, a plurality of splines 117 will project transversely from each opposing side 116b on all keys 116. Inner stator edge 208 is located slightly radially outward from outer circumferential edge 114 of outer race 100. Preferably, stator 200, including the walls of slots 210, is fabricated from a softer material than outer race 100. For example, stator 200 may be fabricated from aluminum, while outer race 100 is fabricated from steel. Stator body 206 is seen surrounding grooves 217.
Before the press fit takes place with outer race 100 and stator 200 axially aligned to be pressed into the assembly, splines 117 extend past the slot 210 sidewalls. During the press fit operation, the harder material of splines 117 cut out and fit into individual transverse grooves 217 from the inner walls of slots 210 resulting in individual splines 117 that are closely fit into grooves 217. This close, transverse fit provides the advantage of preventing stator 200 from pulling away from outer race 100 when the temperature of the torque converter and fluid increases during long term operation of the vehicle. The close fit with in the transverse grooves acts to keep stator 200 and outer race 100 in the same relative positions even while stator 200 expands radially faster than outer race 100 when heated,.
A further advantage is provided by the close fit in that there is very little if any open space between splines 117 and the walls of grooves 217. Therefore, when the torque converter launches (moves) a vehicle from a stopped position, the torque applied to the stator by the fluid returning from the turbine to the pump will create a rotational force in the clutch-locked direction on the stator 200 against outer race 100 preventing rotation of stator 200. Any small spaces or gaps between stator 200 and outer race 100 will result in collisions that wear on the softer stator 200. The close fit between splines 117 of outer race 100 and grooves 217 in stator 200 eliminates or greatly reduces gaps between the contact point between stator 200 and outer race 100 thereby eliminating or greatly reducing the wear on the stator caused by lash.
Thus it is seen that the objects of the invention are efficiently obtained, although changes and modifications to the invention should be readily apparent to those having ordinary skill in the art, which changes would not depart from the spirit and scope of the invention as claimed.
100 outer race
112 outer race body
114 outer circumferential edge
116 keys
116
a outer key edge
116
b opposing side of key
116
c depth (thickness) of key
118 inner circumferential edge
120 strut
122 inclined ramp
124 shoulder
126 roller
128 spring
117 spline
200 stator
202 outer stator edge
204 stator blade
206 stator body
208 inner stator edge
210 stator slot
217 transverse grooves
300 inner race
302 inner race body
304 outer edge of inner race
306 inner edge of inner race
400 stator assembly
This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application No. 61/870,327, filed Aug. 27, 2013, which application is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61870327 | Aug 2013 | US |
