Patent Application
20130255242
The present disclosure relates to an impeller for a torque converter and, more particularly, to an impeller and an associated wear member.
It is often desirable to provide a coupling between the rotating output of a prime mover and the rotating input of a driven load that permits a disparity between the rotational speed of the rotating output of the prime mover and the rotating input of the driven load. For example, in order to permit continuous rotation of the output of the prime mover, even when it is desirable to stop rotation of the input of the driven load, it is desirable to provide a coupling that permits the rotational output of the prime mover to continue despite the input of the driven load being stopped.
An example of such a coupling is a torque converter, which provides a hydrodynamic fluid coupling between the rotating output of a prime mover and the rotating input of a driven load. For example, a machine such as a vehicle may include an internal combustion engine and a transmission, with the output of the internal combustion engine coupled to an input of the transmission by the torque converter.
A torque converter generally includes an input coupling for coupling the output of a prime mover to the input of the torque converter, and an output shaft for coupling the output of the torque converter to a driven load, such as a transmission. The torque converter further includes a housing containing fluid, such as hydraulic fluid. Within the housing, the input coupling is coupled to a pump including an impeller for pumping the fluid in the housing. The torque converter further includes a turbine coupled to the output shaft of the torque converter. The impeller of the pump, driven by the input coupling, pumps fluid through the turbine, thereby causing the turbine to rotate and drive the output shaft of the torque converter and the input of, for example, a transmission. By virtue of the fluid coupling provided by the interaction between the impeller and the turbine, the output of the prime mover may continue to rotate the input coupling of the torque converter, even when the output shaft of the torque converter is stopped.
In conventional torque converters, as a result of various factors, the impeller is an assembly of several parts, including, for example, a rotating housing, an impeller member including blades configured to pump fluid, and a hub member. Rather than being formed as a single piece, these parts are typically secured to one another by fasteners, adhesives, and/or welding. The use of separate parts results from differing requirements associated with the parts and manufacturing limitations. For example, the blades may be formed separately and attached to the impeller member to provide an ability to form blades having complex configurations. The hub member may be formed from relatively stronger materials than the remainder of the impeller in order to account for higher stress and/or wear associated with the hub member during operation of the torque converter. In addition, it may be difficult to form the entire impeller using relatively less expensive processes such as casting due to the relatively complex shape of the parts. As a result, it may be relatively costly to manufacture and assemble the impeller. Maintenance costs associated with the torque converter may also increase due to these limitations. As a result of potential drawbacks such as those mentioned above, it may be desirable to provide an impeller for a torque converter that is less costly to manufacture and maintain, but which still provides desired operation and service life characteristics.
An example of torque converter parts formed via casting is described in U.S. Patent Application No. US 2004/0062650 to Makim et al. (“the '650 application”). In particular, the '650 application discloses an assembly for a fluid coupling that includes a hub having a body portion defining a central bore therethrough, with a radially extending flange extending from the body portion. The hub is formed of a material that has a higher melting temperature than aluminum, and a wheel having an outer shell portion is cast about the radially extending flange. The wheel has an integrally cast set of blades, with the outer shell and blades made of aluminum.
Although the assembly disclosed in the '650 application may provide some advantages relative to some conventional assemblies, it may suffer from a number of possible drawbacks. For example, due to the multiple casting processes required for manufacturing the assembly, it may be undesirably costly and complicated to produce. Further, due to the different materials included in the assembly, potential problems associated with securing the parts of the assembly together may result in a relative lack of durability. The torque converter and method disclosed herein may be directed to mitigating or overcoming these and other possible drawbacks.
In one aspect, the present disclosure includes an impeller for a torque converter. The impeller includes a rotating housing portion configured to be driven by a prime mover, a blade portion including a plurality of blades configured to create fluid flow for pumping fluid to a turbine of the torque converter, and an impeller hub portion configured to couple the impeller to the torque converter and rotate about an output shaft of the torque converter. The impeller hub portion defines an inner surface having an annular recess, and at least one inlet passage and at least one outlet passage configured to provide flow paths for fluid entering and exiting the impeller. The torque converter further includes an annular wear member at least partially received in the annular recess of the impeller hub portion, wherein the annular wear member is formed from a ferrous material. The rotating housing portion, the blade portion, and the impeller hub portion are integrally formed as a single piece casting.
In another aspect, the present disclosure includes a torque converter including an impeller configured to be rotated by a prime mover and pump fluid, a turbine configured to rotate as a result of fluid pumped by the impeller, and an output shaft coupled to the turbine and configured to be rotated by the turbine. The impeller includes a rotating housing portion configured to be driven by the prime mover, a blade portion including a plurality of blades configured to create fluid flow for pumping fluid to the turbine, and an impeller hub portion coupling the impeller to the torque converter such that the impeller rotates about the output shaft. The impeller hub portion defines an inner surface having an annular recess, and at least one inlet passage and at least one outlet passage configured to provide flow paths for fluid entering and exiting the impeller. The torque converter further includes an annular wear member at least partially received in the annular recess of the impeller hub portion. The annular wear member is formed from a ferrous material, and the rotating housing portion, the blade portion, and the impeller hub portion are integrally formed as a single piece casting.
In still a further aspect, the present disclosure includes a method for producing an impeller for a torque converter. The method includes casting as a single piece, an impeller for the torque converter. The impeller includes a rotating housing portion configured to be driven by a prime mover, a blade portion including a plurality of blades configured to create fluid flow for pumping fluid to a turbine of the torque converter, and an impeller hub portion configured to couple the impeller to the torque converter and rotate about an output shaft of the torque converter, wherein the impeller hub portion defines an inner surface having an annular recess. The method further includes boring at least one inlet passage in the impeller hub portion and boring at least one outlet passage in the impeller hub portion. Casting the impeller includes forming the impeller onto an annular wear member formed of a ferrous material, such that the annular wear member is retained by the annular recess of the impeller hub portion.
In the exemplary embodiment shown in
During operation, prime mover 14 rotates flywheel 24, which is coupled to rotating housing 26 of torque converter 10, thereby driving rotating housing 26. Impeller 36 of pump 34, being coupled to rotating housing 26, rotates about output shaft 28 and pumps fluid through turbine 38. Turbine 38 includes a plurality of vanes 44 configured to rotate turbine 38 about longitudinal axis X as fluid flows through vanes 44. Turbine 38, by virtue of being coupled to output shaft 28 of torque converter 10, drives output shaft 28, which is coupled to driven mechanism 18 by output yoke 30. Thus, the interaction of the fluid being pumped through turbine 38 by impeller 36 provides a hydrodynamic fluid coupling between prime mover 14 and driven mechanism 18.
The hydrodynamic fluid coupling permits output 12 of prime mover 14 to rotate at a different speed than input member 16 of driven mechanism 18. For example, for machines such as vehicles, prime mover 14 may operate at a relatively low speed while input member 16 of the transmission is held in a stopped condition (e.g., by operation of brakes of the vehicle). Pump 34 of torque converter 10 pumps fluid through turbine 38, but by holding input member 16 in a stopped condition, the energy of the pumped fluid can be absorbed by heating of the fluid rather than turning turbine 38. However, if input member is no longer held in a stopped condition, fluid pumped through turbine 38 causes it to rotate, thereby rotating output shaft 28 of torque converter 10. As the speed of output 12 of prime mover 14 is increased, pump 34 of torque converter 10 pumps fluid through turbine 38 at an increasing rate, thereby causing turbine 38 and output shaft 28 to rotate at an increasing rate.
In the exemplary embodiment shown, output shaft 28 rotates about longitudinal axis X on bearings 42. Housing 32 includes a lubricating passage 46 configured to supply the bearing 42 located at the end of output shaft 28 adjacent output yoke 30 of torque converter 10. Lubricant may be provided under pressure to ensure sufficient lubrication and cooling of bearing 42. For example, lubricant may be supplied to bearing 42 at about 70 pounds per square inch (psi).
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In the exemplary embodiment shown, rotating housing portion 36a defines an outer surface 53 and an inner surface 54. Inner surface 54 defines a curved annular cavity 56, which curves through an apex 58 relative to longitudinal axis X, and around toward a portion of turbine 38, such that an end 60 of inner surface 54 it closer to longitudinal axis X than apex 58. As impeller 36 rotates, fluid flows in cavity 56 from a portion of cavity 56 closer to impeller hub portion 36c toward apex 58 and into turbine 38.
Blade portion 36b of exemplary impeller 36 is within rotating housing portion 36a, with blade portion 36b including an inner wall 62. Blades 48 extend from inner surface 54 of rotating housing portion 36a to inner wall 62.
Impeller hub portion 36c of exemplary impeller 36 defines an inner surface 64 extending around a sleeve 66 supporting stator 40. Sleeve 66 does not rotate, and impeller 36 rotates about sleeve 66 on bearing 42 associated with lock-up clutch assembly 52 and bearing 68 (e.g., a roller bearing) between sleeve 66 and a coupling member 70 (e.g., a gear) to which a longitudinal end of impeller hub portion 36c is coupled via one or more fasteners 72 (e.g., such as one or more bolts) (see
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According to some embodiments, annular wear member 86 (or end face 90 thereof) may be formed from a relatively hard material configured to exhibit reduced wear caused by sliding motion of seal member 78 against end face 90. For example, wear member 86, or end face 90, may be formed from a ferrous material, such as, for example, steel or cast iron, or any other suitable material known to those skilled in the art.
According to some embodiments, impeller 36 is formed by casting rotating housing portion 36a, blade portion 36b, and impeller hub portion 36c onto wear member 86, for example, such that wear member 86 may be retained in annular recess 82 of impeller hub portion 36c without adhesives, welding, or fasteners. For example, wear member 86 may be formed prior to casting impeller 36, and wear member 86 may be placed in a casting mold used for forming impeller 36 prior to supplying the molten casting material into the mold. Thereafter, the molten casting material may be poured into the mold, and after the molten casting material cools, wear member 86 is retained in annular recess 82. According to some embodiments, annular recess 82 and/or wear member 86 may be configured to enhance the retention of wear member 86 in annular recess 82, for example, by provision of protrusions, grooves, etc., on ridge 88 of wear member 86 for improving engagement between ridge 88 and annular recess 82.
According to some embodiments, the casting material used to form impeller 36 may include aluminum and alloys thereof, and wear member 86 may be formed from a ferrous material such as steel or cast iron. By virtue of wear member 86 being steel or cast iron, which typically has a higher melting temperature than aluminum, and the casting material being aluminum, the material of wear member 86 will not be significantly softened or melt when the molten aluminum is poured into the casting mold.
As shown
According to some embodiments, inlet passage(s) 92 and/or outlet passage(s) 94 of impeller hub portion 36c may be formed by boring passages into impeller hub portion 36c. For example, after impeller 36 is cast, inlet passage(s) 92 may be bored into impeller hub portion 36c by boring a passage or passages from an inner diameter of impeller hub portion 36c in a radial direction toward blade portion 36b. Outlet passage(s) 94 may be bored into impeller hub portion 36c by boring a passage or passages from an inner diameter of impeller hub portion 36c in a radial direction toward blade portion 36b, and boring a passage or passages from blade portion 36b in a longitudinal direction toward the passage(s) bored in the radial direction until the two bored passages meet to form first portion 94a and second portion 94b of outlet passages 94.
According to some embodiments, torque converter 10 may result in improved performance and reduced materials and manufacturing costs. For example, by virtue of the parts of exemplary impeller 36 being formed of a relatively lightweight material, such as aluminum, impeller 36 may provide improved performance resulting from reduced weight and inertia. This may result in more efficient operation of prime mover 14 coupled to torque converter 10 and quicker response by impeller 36. In addition, exemplary wear member 86 provides impeller 36 with improved durability. Because impeller 36 is formed from a lightweight material such as aluminum, such lightweight materials may not be able to withstand heat and wear associated with a seal member sliding against the lightweight material. By virtue of wear member 86 being formed from a material resistant to wear, excessive wear may be avoided, even though impeller 36 may be formed from a less durable material.
Exemplary torque converter 10 may also provide reduced material and manufacturing costs. For example, by forming impeller 36 from a relatively less expensive material such as aluminum, impeller 36 may be relatively less expensive to manufacture. In addition, because impeller 36 is cast as a single piece, the number of parts for assembly of torque converter 10 may be greatly reduced, thereby resulting in reduced assembly and labor costs.
It will be apparent to those skilled in the art that various modifications and variations can be made to the exemplary disclosed systems and methods. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the exemplary disclosed embodiments. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.
