Structural support member for stator retention and method of assembling an electromechanical transmission

An electromechanical transmission includes a motor/generator having a stator and a rotor and including a structural support member that supports the stator in fixed relation thereto and the rotor in rotational relation thereto. By supporting both the stator and the rotor, the structural support member substantially controls a spatial relationship (i.e., the gap in which a magnetic field is created) between the stator and rotor.

TECHNICAL FIELD

This invention relates to support and assembly of a motor/generator for an electromechanical transmission.

BACKGROUND OF THE INVENTION

A hybrid electromechanical vehicular transmission utilizes interactive planetary gear arrangements that are operatively connected to an engine and two motor/generators. Selective utilization of torque transfer devices enables power transfer via the planetary gear arrangements from the engine and/or motor/generators to the output member of the transmission.

A power transmission in an electromechanical transmission is described in commonly owned U.S. Provisional Application No. 60/590,427 entitled Electrically Variable Transmission with Selective Fixed Ratio Operation, filed Jul. 22, 2004, and hereby incorporated by reference in its entirety.

Motor/generators in an electromechanical transmission are typically cooled by directing transmission fluid from a fluid source such as a pump to the motor/generators. A cooling system that requires a minimum of added machining and assembly steps, added components and minimal or no increase in pump capacity is desirable.

SUMMARY OF THE INVENTION

The invention provides novel stator and rotor support and packaging to enable reliable positioning of the stator and rotor with minimal relative variation. Pursuant to the invention, an electromechanical transmission includes a motor/generator having a stator and a rotor and including a structural support member that at least partially supports the stator in a fixed relationship and the rotor in a rotational relationship. By supporting both the stator and the rotor, the structural support member substantially controls a spatial relationship (i.e., the gap in which a magnetic field is created and which allows relative movement) between the stator and rotor.

In one aspect of the invention, the structural support member is an end cover that partially encloses the rotor and the stator within an interior space of the transmission. Alternatively, the structural support member may be a center support located within the interior space for supporting a more inwardly-located motor/generator. An end cover-type structural support member and a center support-type structural support member may be used together in one transmission to each respectively support a stator and a rotor of a first and a second motor/generator, respectively. In that instance, the end cover-type structural support member and the center support-type structural support member may respectively support rotor hubs of the motor/generators with respect to a common grounding member, such as a transmission case. Because the rotor hubs are supported with respect to a common grounding member, radial loads resulting from the two motors are balanced.

In another aspect of the invention, a rotor hub that is connected to and rotates with the rotor is at least partially supported by the structural support member. Preferably, a bearing is located between the structural support member and the rotor hub. Accordingly, the gap in which the magnetic field between the stator and the rotor is created is dependent only upon dimensional tolerances of the structural support member, the stator, the rotor, the rotor hub and the bearing.

In a further aspect of the invention, the structural support member is made of iron. Because a portion of the structural support member is located radially outward of the stator and a portion is located radially inward of the rotor, the iron supplements magnets in the stator to increase the magnetivity of the motor/generator, thereby increasing torque capacity. Additionally, because the iron structural support member has the same thermal expansion properties as the iron in the motors, the spatial relationship of the stator to the rotor is maintained despite thermal expansion.

In another aspect of the invention, an annular stator support is rigidly connected to and supported by the structural support member. The stator is supported by the annular stator support. The annular stator support is located radially outward of the stator. At least a portion of the structural support member is located radially inward of the rotor. Preferably, both the annular stator support member and the structural support member are iron, to increase magnetivity and torque capacity of the motor/generator, as described above.

The invention also provides a motor/generator module that may be preassembled before attachment to the rest of the transmission. The module includes the structural support member, the stator, the rotor and the rotor hub. By preassembling these components, the gap is determined and may be more easily inspected for compliance purposes prior to final installation of the module.

A method of assembling an electromechanical transmission includes providing the structural support member, the rotor hub and the bearing. The rotor hub is connected to the structural support member in rotatable relationship thereto with the bearing disposed between the structural support member and the rotor hub. The rotor is connected to the rotor hub. The stator is press-fit to the structural support member to form a motor/generator module. The entire module is then guided onto a shaft of the transmission.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Exemplary Embodiment

Motor Cooling System

Referring to the drawings wherein like reference numbers refer to like components,FIG. 1shows a vehicle10having an electro-mechanical transmission11. An input shaft12is disposed about a center axis14and is operable for transferring power from an engine (not shown) to the transmission11. A main shaft16is longitudinally disposed and rotatable about the center axis14and is engageable with the input shaft12. The engagement of one or more of a plurality of clutches such as clutch15interconnects one or more of a plurality of planetary gear sets such as planetary gear set17to transfer power at varying ratios to an output member18. Two electric motor/generators20A and20B are coaxially oriented about the center axis14. Each motor/generator20A,20B is selectively operatively connectable to a member of one of the planetary gear sets to provide a range of continuously variable speed ratios between the input shaft12and the output member18, as will be readily understood by those skilled in the art. Each of the motor/generators20A,20B includes a respective generally ring-shaped stator22A,22B and a generally ring-shaped rotor24A,24B, respectively, rotatable with respect to the respective stator22A,22B. An end cover26is mounted with respect to the main shaft16. The end cover26partially encases the motor/generators20A,20B within and partially defines an interior space28. The end cover26cooperates with a first portion30of a housing member (i.e., an upper portion of a transmission case) and a second portion32of the housing member (i.e., a lower portion of the transmission case) to further encase the motors/generators20A,20B within the interior space28. An O-ring33helps to seal the interface between the end cover26and the first and second portions30,32of the housing member.

Referring now toFIG. 2, the end cover26is formed with first and second annular recesses34,36, respectively. Furthermore, a first flow passage38is bored through the end cover26to create a fluid communication between the first annular recess34and a second flow passage40formed in the first portion30of the housing member. A valve body42is in fluid communication with a fluid source such as a pump (not shown) and is capable of delivering pressurized fluid via the second flow passage40to the first flow passage38from which the fluid flows to the first annular recess34. For illustrative purposes, the valve body42is shown directly adjacent to the second flow passage40in housing cavity43; however, the valve body42may be more remotely located and connected via hydraulic passages to the second flow passage40. Additionally, the fluid source or pump may be located anywhere on the vehicle and fluidly connected with the valve body42, as will be understood by those skilled in the art.

As may be better viewed inFIG. 3, a ring-shaped sleeve44A is press fit to an inner surface45of the end cover26. The ring-shaped sleeve44A includes a plurality of circumferentially-spaced radial openings46A that permit fluid communication between the first annular recess34and the interior space28. Specifically, the circumferentially-spaced radial openings46A direct fluid onto first end (i.e., left side) stator windings48B of the stator22B to cool the windings48B. The circumferentially-spaced radial openings46A may be designed to present the fluid in the form of a mist over the stator windings48B to prevent wear associated with high velocity fluid spray (e.g., by varying the diameter of the openings or by tapering the openings). Alternatively, nozzles may be fit within the radially-spaced openings46A and configured to present the fluid in the form of a mist. Yet another alternative is to connect a deflector49to the end cover26or to the ring shaped sleeve44A to deflect fluid flowing from the circumferentially-spaced radial openings46A, thereby slowing the velocity of the fluid prior to the fluid contacting the windings48B. The deflector49may be a steel flange. A single, ring-shaped deflector may be used or separate deflectors49may be placed under each respective circumferentially-spaced radial opening46A.

Referring again toFIG. 2, the second annular recess36is in fluid communication with the second flow passage40. Furthermore, a second set of circumferentially-spaced radial openings46B are formed in the end cover26such that they are in fluid communication with the second annular recess36. Pressurized fluid from the fluid source flows from the valve body42through the second flow passage40and the second annular recess36to the circumferentially-spaced radial openings46B and onto the second end (i.e., right side) stator windings50B for cooling thereof. As with the first set of circumferentially-spaced radial openings46A, the second set of circumferentially-spaced radial openings46B may be configured to supply fluid to the second end stator winding50B in the form of a mist.

A center support54is rigidly supported with respect to the main shaft16′ about the center axis14and supports the stator22A as described below. A third flow passage56is formed within the center support54and is in fluid communication with the valve body42through a fourth flow passage58formed in the first portion30of the transmission case. Cooling fluid is supplied to first end (i.e., left side) stator windings48A of the stator22A via the third and fourth flow passages56,58. A drilled bore55in the center support54intersects an annular cavity57. An annular plate59having an orifice61is press fit into the cavity57. Fluid flows from the third passage56, into the bore55, into the cavity57and through the orifice61to cool the first end stator windings448A. The center support54is formed with a third annular recess60which is in fluid communication with a third set of circumferentially-spaced radial openings62which are also formed in the center support54. Cooling fluid is supplied to second end (i.e., right side) stator windings50A of the stator22A from the valve body42via a fifth flow passage64in fluid communication with the third annular recess60and through the third set of circumferentially-spaced radial openings62.

Referring toFIGS. 2-3, a motor cooling system66for the motor/generator20B includes the end cover26having the first flow passage38and being formed with first and second annular recesses34,36, respectively. Furthermore, the motor cooling system66may include the ring-shaped sleeve44A having the first set of circumferentially-spaced radial openings46A for cooling the left side stator windings48B. The motor cooling system66may also include the second set of radially-spaced openings46B formed in the end cover26to provide fluid communication between the second annular recess36and the right side stator windings50B for cooling thereof via fluid provided from a fluid source.

Stator Support and Motor/Generator Packaging Module

Referring toFIG. 2, the stator22B includes a plurality of segmented portions (one portion shown) spaced about an inner surface68of the end cover26. Those skilled in the art will readily understand the segmented nature of the stator22B. The inner surface68of the end cover26may be provided with slots coordinating with extensions on the segmented portions of the stator22B for fixedly connecting the segments to the end cover26.

A first rotor hub70B is rotatably supported by the end cover26at a bearing72B and is welded to the main shaft16. The rotor24B is rigidly connected to the first rotor hub70B and is rotatable therewith with respect to the end cover26. A gap74B is achieved between the stator22B and the rotor24B and is controlled by the radial dimensions of the rotor24B and the stator22B and the distance between an exterior surface76of the first rotor hub70B and the inner surface68of the end cover26. Because the rotor hub70B is mounted at the shaft bearing72B and is supported by the end cover26which also forms the inner surface68, variability in the gap74B due to build tolerances is minimized (i.e., the dimensions of one element, the end cover26, influence the positioning and dimensional play at both ends (the exterior surface76of the first rotor hub70B and the inner surface68of the end cover26) of the space in which the motor/generator20B is packaged).

The stator22A includes a plurality of segmented portions spaced about an inner surface78of the center support member54. The inner surface78of the center support member54may be provided with slots coordinating with extensions on the segmented portions of the stator22A for fixedly connecting the segments to the center support member54.

A second rotor hub70A consists of welded outer portion71and inner portion73. The rotor24A is rigidly connected to the second rotor hub70A and is rotatable therewith with respect to the center support54. The second rotor hub70A is partially supported by the center support54at bearing72A. A gap74A is achieved between the stator22A and the rotor24A and is controlled by the radial dimensions of the rotor24A and the stator22A and the distance between an outer surface80of the second rotor hub70A and the inner surface78of the center support member54. Because the second rotor hub70A is supported by the center support member54, the dimensions of one component (the center support member54) influence the positioning and dimensional play at both ends (i.e., the inner side78of the center support member54and the exterior surface80of the rotor hub70A) of the space in which the motor/generator20A is packaged.

Support of the rotor24B is further provided by bearing75B, disposed between the shaft16and the rotor hub70A, because the weight of the motor20B and rotor hub70B are distributed to the shaft16since the rotor hub70B is welded to the shaft16. Likewise, support of the rotor24A is further provided by shaft bearing75A disposed between the rotor hub70A and the center support54. Thus, support of the rotors24A,24B is cantilevered, rather than provided on either side of each rotor, as is typically done. The rotors24A and24B are both grounded or steadied by a common member, the shaft16. Rotor24B is steadied by the shaft16because the rotor hub70B is welded to it. Rotor24A is steadied by the shaft16via the shaft bearing75B. By supporting the rotors24A,24B at a common member (the shaft16), unintended run out between the rotors24A,24B is minimized.

Because for each motor/generator20A and20B, the rotor24A,24B and stator22A,22B are supported by a common member (the center support54and end cover26, respectively) the invention allows each motor/generator20A,20B to be easily prepackaged as a module prior to attachment with the transmission11. The motor/generator module82for motor/generator20B includes the end cover26having the stator22B fit at the inner surface68. The rotor24B is rigidly connected to the rotor hub70B, which is then fit to the end cover26at the bearing72B. The entire module82(end cover26, stator22B, rotor24B, bearing72B and rotor hub70B) may then be piloted on to the shaft16and welded thereto as a unit. Similarly, the motor/generator module84for motor/generator20A includes the center support54having stator22A fit at the inner surface78. The rotor24A is rigidly connected to the rotor hub70A, which is then fit to the center support54at bearing72A and bearing75A. The entire module84(which includes center support54, stator22A, rotor24A and rotor hub70A) may then be piloted on to the shaft16over bearing75B as a unit.

The end cover26as well as the center support54may be iron. By forming these components from iron, magnetivity of the motor/generators20A and20B is increased as the iron in the end cover26and the center support54(which will be disposed both above the stators and below the rotors) supplements the magnets in the respective motor/generators20B,20A to increase torque capacity.

Second Exemplary Embodiment

Motor Cooling System

Referring toFIG. 4, a vehicle10′ includes an electro-mechanical transmission11′, An input shaft12′ is disposed about a center axis14′ and is operable for transferring power from an engine (not shown) to the transmission11′. A main shaft16′ is longitudinally disposed and rotatable about the center axis14′ and is engageable with the input shaft12′. The engagement of one or more of a plurality of clutches such as clutch15′ interconnects one or more of a plurality of planetary gear sets such as planetary gear set17′ to transfer power at varying ratios to an output member (not shown, but situated similarly to output member18ofFIG. 1). Two electric motor/generators20A′ and20B′ are coaxially oriented about the center axis14′. Each motor/generator20A′,20B′ is selectively operatively connectable to a member of one of the planetary gear sets to provide a range of continuously variable speed ratios between the input shaft12′ and the output member, as will be readily understood by those skilled in the art. Each of the motor/generators20A′,20B′includes a generally ring-shaped stator22A′,22B′ and a generally ring-shaped rotor24A′,24B′, respectively, rotatable with respect to the respective stator22A′,22B′. An end cover26′ is mounted with respect to the main shaft16′. The end cover26′ partially encases the motor/generators20A′,20B′ within and partially defines an interior space28′. The end cover26′ includes a first annular stator support86A′. The stat or support86A′ is bolted to the end cover26′ with bolt87and cooperates with a first portion30′ of a housing member (i.e., an upper portion of a transmission case) and a second portion32′ of the housing member (i.e., a lower portion of the transmission case) to further encase the motors/generators20A′,20B′ within the interior space28′. The first annular stator support86A′ is formed with a notched portion89which aids in positioning the stator22B′. The stator22B′ is held in position against the notched portion87to prevent movement of the stator22B′ due to magnetic forces.

The first annular stator support86A′ is formed with an annular recess36′. Furthermore, flow passage40′ is formed in the first portion30′ of the housing member. A valve body42′ is in fluid communication with a fluid source such as a pump (not shown) and is capable of delivering pressurized fluid via the flow passage40′ to the annular recess36′. For illustrative purposes, the valve body42′ is shown directly adjacent to the flow passage40′; however, the valve body42′ may be more remotely located and connected via hydraulic passages to the flow passage40′. An o-ring33′ is disposed between the first portion of the housing30′ and the first annular stator support86A′ to help prevent leakage of fluid from a space formed between the annular recess36′ and the first portion30′ of the housing. Additionally, the fluid source or pump may be located anywhere on the vehicle and fluidly connected with the valve body42′, as will be understood by those skilled in the art.

A plurality of circumferentially-spaced radial openings46A′ are formed in first the annular stator support86A′ to permit fluid communication between the annular recess36′ and the interior space28′. Specifically, the circumferentially-spaced radial openings46A′ direct fluid onto first end (i.e., left side) stator windings48B′ of the stator22B′ to cool the windings48B′. The circumferentially-spaced radial openings46A′ may be designed to present the fluid in the form of a mist over the stator windings48B′ to prevent wear associated with high velocity fluid spray (e.g., by varying the diameter of the openings or by tapering the openings). Alternatively, nozzles may be fit within the radially-spaced openings46A′ and configured to present the fluid in the form of a mist. Yet another alternative is to connect a deflector to the end cover26′ or to the first annular stator support86A′, positioned adjacent to the circumferentially-spaced radial openings46A′ similarly to the positioning of deflector49ofFIG. 3, to deflect fluid flowing from the circumferentially-spaced radial openings46A′, thereby slowing the velocity of the fluid prior to the fluid contacting the windings48B′. The deflector may be a steel flange. A single, ring-shaped deflector may be used or a separate deflector may be placed under each respective circumferentially-spaced radial opening46A′.

A second set of circumferentially-spaced radial openings46B′ are formed in the first annular stator support86A′ such that they are in fluid communication with the annular recess36′. Pressurized fluid from the fluid source flows from the valve body42′ through the flow passage40′ and the annular recess36′ to the circumferentially-spaced radial openings46B′ and onto the second end (i.e., right side) stator windings50B′ for cooling thereof. As with the first set of circumferentially-spaced radial openings46A′, the second set of circumferentially-spaced radial openings46B′ may be configured to supply fluid to the second end stator winding50B′ in the form of a mist.

A center support54′ is rigidly supported with respect to the main shaft16′ about the center axis14′. A second annular stator support86B′ is welded to a support element88which in turn is bolted to the center support54′ via90A and90B. Bolt90A also connects both the support element88and the second annular stator support86B′ to the first portion30′ of the housing member. Alternatively, the second annular stator support86B′ and the support element88may be formed as a unitary component. A fourth flow passage58′ and a fifth flow passage64′ are formed in the first portion30′ of the transmission case in fluid communication with the valve body42′. Sixth and seventh flow passages65,67are formed in the second annular stator support86B′ in fluid communication with the fourth and fifth flow passages58′,64′, respectively. First and second ring-shaped sleeves or annular spray rings44B,44C are press-fit against an inner surface94of the first portion30′ of the housing member. A third set62′ and a fourth set96of circumferentially-spaced radial openings are formed in the respective annular spray rings44C,44B, such that they are in fluid communication with the seventh and sixth flow passages67,65, respectively, of the second annular stator support86B′. Cooling fluid is supplied to first end (i.e., left side) stator windings48A′ of the stator22A′ via the fourth and sixth flow passages58′ and the fourth set of circumferentially-spaced radial openings96. Cooling fluid is supplied to second end (i.e., right side) stator windings50A′ of the stator22A′ from the valve body42via a fifth flow passage64′ in fluid communication with the seventh flow passage67through the third set of circumferentially-spaced radial openings62′.

A motor cooling system66′ for the motor/generator20B′ includes the second annular stator support86B′ having the sixth and seventh flow passages65,67. Furthermore, the motor cooling system66′ may include the ring-shaped sleeves44B,44C having the fourth and third sets of radially-spaced openings96,62′ for cooling the left side and right side stator windings48A′,50A′, respectively.

To assemble the motor/generator20A′ within the transmission11′, the support element88is bolted to the center support54′. The second annular stator support86B′ is press fit against the inner surface94of the first portion30′ of the housing member in the interior cavity space28′. The ring sleeves44B,44C are press fit against the second annular stator support86B′. The stator22A′ is then press fit against the inner surface97B′ of the second annular stator support86B′ between the spray rings44B,44C.

Stator Support and Motor/Generator Packaging Module

Referring toFIG. 4, the stator22B′ includes a plurality of segmented portions spaced about an inner surface97B of the first annular stator support86A′. The inner surface97B may be provided with slots coordinating with extensions on the segmented portions of the stator22B′ for fixedly connecting the segments to the annular stator support86A′.

A first rotor hub70B′ is rotatably supported by the end cover26′ at a bearing72B′ and is welded to the main shaft16′. The rotor24B′ is rigidly connected to the first rotor hub70B′ and is rotatable therewith with respect to the end cover26′. A gap74B′ is achieved between the stator22B′ and the rotor24B′ and is controlled by the radial dimensions of the rotor24B′ and the stator22B′ and the distance between an exterior surface76′ of the first rotor hub70B′ and the inner surface97B of the annular stator support86A′. Because the rotor hub70B′ is mounted at the shaft bearing72B′ which is supported by the end cover26′, and because the end cover26′ also supports the annular stator support86A′ which forms the inner surface97B, variability in the gap74B′ due to build tolerances is minimized.

The stator22A′ includes a plurality of segmented portions spaced about an inner surface97A of the second annular stator support86B′. The inner surface97A may be provided with slots coordinating with extensions on the segmented portions of the stator22A′ for fixedly connecting the segments to the annular stator support86B′.

The rotor24A′ is rigidly connected to a second rotor hub70A′ and is rotatable therewith with respect to the center support54′. The second rotor hub70A′ is partially supported by the center support54′ at bearing72A′. A gap74A′ is achieved between the stator22A′ and the rotor24A′ and is controlled by the radial dimensions of the rotor24A′ and the stator22A′ and the distance between an outer surface80′ of the second rotor hub70A and an inner surface97A of the annular stator support86B′.

Support of the rotor24B′ is further provided by bearing72C via a rotor flange99B welded to the rotor hub70B′. Likewise, support of the rotor24A′ is further provided by bearing72D via a rotor flange99A welded to the rotor hub70A′. Bearing72D is support by separate structure, as shown inFIG. 4. Support of the rotor24A′ is further provided by shaft bearing75A′ disposed between the rotor hub70A′ and the center support54′.

Because for each motor/generator20A′ and20B′, the rotor24A′,24B′and stator22A′,22B′ are supported by a common member (the center support54′ and end cover26′, respectively) the invention allows each motor/generator20A′,20B′ to be easily prepackaged as a module prior to attachment with the transmission11. The motor/generator module82′ for motor/generator20B′ includes the end cover26′ and the first annular stator support86A′ having the stator22B′ fit at the inner surface97B. The rotor24B′ is rigidly connected to the rotor hub70B′, which is then fit to the end cover26′ at the bearing72B′. The entire module82′ (end cover26′, stator22B′, rotor24B′, rotor hub70B′ and rotor flange99B) may then be piloted on to the shaft16′ and welded thereto as a unit. Similarly, the motor/generator module84′ for motor/generator20A′ includes the center support54′ and the second annular stator support86B′having stator22A′ fit at the inner surface97A. The rotor24A′ is rigidly connected to the rotor hub70A′, which is then fit to the center support54′ at bearing72A′. The entire module84′ (which includes center support54′, bearing72D, bearing72A′, the annular stator support86A′, stator22A′, ring-shaped sleeves44B,44C, rotor24A′, rotor hub70A′ and rotor flange99A) may then be piloted on to the shaft16as a unit.

The end cover26′ as well as the center support54′ may be iron. By forming these components from iron, magnetivity of the motor/generators20A′ and20B′ is increased as the iron in the end cover26′ and the center support54′ (which will be disposed both above the stators and below the rotors) supplements the magnets in the respective motor/generators20B′,20A′ to increase torque capacity.