Motor support for a hybrid electric transmission

Motor bracket for hybrid electric transmission

Technical field

[0001] The present invention relates to a power system for a hybrid electric vehicle, and more particularly to a rotor and a stator that support an electric machine to create and maintain a precise air gap therebetween.

Background technique

[0002] Hybrid electric vehicles (HEVs) have an internal combustion engine and an electric motor that can be used to propel the vehicle alternately or in combination. A variety of different drive trains are used in hybrid vehicles. The present invention relates to a parallel configuration in which an engine is coupled to an electric motor via a disconnect clutch that drives a torque converter input of an automatic hydraulic transmission. The hydraulic transmission has an output connected to a differential coupled to two drive wheels of the vehicle. The drive train power flow arrangement of such parallel hybrid electric vehicles is known in the art.

[0003] The problem faced by HEV designers is how to cool the split clutch and the rotor and stator portions of the motor. Various air and liquid based cooling systems have been proposed; however, most systems are expensive and cause assembly problems when attempting to convert a non-hybrid vehicle into a hybrid mode of operation. Separate clutches, electric motors, torque converters, and automatic transmissions need to be packaged in a compact manner so that conventional vehicles can be reconfigured as hybrid systems at relatively low cost and with little vehicle body variation or no vehicle body changes at all. .

Summary of the invention

An assembly for an electric motor for supporting a vehicle power system, comprising: a casing, a stator fixed to the casing, a bearing having a radial position determined by the casing, an assembly of the contact bearing, and a rotor fixed to the assembly The rotor includes a radially outer surface that is radially spaced from the stator by an air gap, the air gap being determined by contact between the bearing and the assembly. The present invention relates to a novel hybrid electric vehicle and a plurality of novel components and sub-assemblies that are particularly suitable for relocating separate clutches and electric motors within the wet side of an automatic transmission. This is done without changing the conventional power flow of the engine, disconnect clutch, electric motor, torque converter, and transmission connected in series.

The present invention provides a transmission housing that connects the engine to the input side of a disconnect clutch that is repositioned in an automatic transmission housing, rather than connecting the torque converter directly to the engine as typically in a non-hybrid vehicle. The drive housing forms an annular cavity of sufficient size to accommodate the torque converter. The electric motor is also located in the wet zone of the automatic transmission, which preferably surrounds the disconnect clutch. The rotor of the motor is connected to the output of the disconnect clutch. Both the split clutch output and the rotor are coupled to a rotor shaft that is coupled to the input turbine of the torque converter. The torque converter stator and the output turbine are coupled to the tubular stator shaft and the transmission input shaft, respectively. The transmission input shaft, stator shaft, rotor shaft, and split clutch hub are all concentric with each other and can be utilized by an annular opening on the front side of the automatic transmission housing.

Similar to conventional torque converters, the torque converter and the transmission housing can be removably mounted in front of the transmission housing. Instead of connecting the torque converter to the engine mounting plate, connect the drive housing to the mounting plate. The torque converter is free to rotate relative to the transmission housing within the transmission housing to form a compact and axially short motor/transmission assembly. By placing the disconnect clutch and motor coaxially in front of the wet zone of the automatic transmission, the transmission hydraulic fluid pump, associated pump and piping system can cool the split clutch and motor with a relatively small increase in axial length. Rotor and stator sections.

[0008] Although generally similar to conventional torque converters, the torque converter has been uniquely modified to implement the present invention. Since the torque converter is not connected to the engine mounting plate, no mounting studs are provided on the housing of the torque converter. Rather, a central axial bearing assembly is provided that cooperates with an engine mounting plate having a corresponding bearing assembly to radially support the torque converter and axially limit movement in the forward direction. Inside the torque converter is a back facing the thrust bearing assembly that cooperates with the free end of the transmission input shaft to limit axial movement of the torque converter in a rearward direction.

In order to implement the invention, the transmission housing is preferably also uniquely modified. The transmission housing includes a wet outer casing that defines a closed wet zone and a torque converter housing that is modified to have one side secured to the wet outer casing and the other side secured to the engine block. The torque converter housing has a rear wall that forms a boundary between the wet chamber and the drying chamber, wherein the torque converter and the transmission housing are oriented. The rear wall defines an annular bore that cooperates with the disconnect clutch input hub to support the input hub and rotor shaft with the associated rotor portion of the motor and the disconnect clutch output hub.

DRAWINGS

1 is a schematic diagram of a hybrid electric vehicle having a parallel power flow design;

2 is a simplified schematic view of a repositioned split clutch and electric motor in accordance with the present invention; [0011] FIG.

3 is a simplified cross-sectional view of the automatic motor/transmission assembly of the present invention;

4a is a more detailed cross-sectional side elevational view of the automatic motor/transmission assembly of the present invention; [0013] FIG.

Figure 4b is a symbolic view of the motor/transmission assembly of Figure 4a;

[0015] FIG. 4c is a clutch application table of each of six forward gears and reverse gears;

[0016] FIG. 5 is an enlarged plan view of a cross section of a torque converter in cooperation with a disconnect clutch and an electric motor;

Figure 6 is an enlarged plan view of the disconnect clutch and the motor;

[0018] FIG. 7 is an enlarged view of the engine output and the transmission input shaft on the mounting plate torque converter, showing their axial directions;

Figure 8 is a perspective view of a mounting plate for practicing the present invention;

Figure 9 is a perspective view of a torque converter for practicing the present invention;

[0021] FIG. 10 is a perspective view of a transmission case;

[0022] FIG. 11 is a view of an alternative embodiment of a transmission housing with a packaged torque converter;

[0023] Figure 12 is a side cross-sectional view of a portion of a vehicle powertrain located above a central axis;

[0024] FIG. 13 is a plan view of the terminal block assembly;

[0025] FIG. 14 is a side cross-sectional view of a portion of a vehicle powertrain located below a central axis;

15 is a side cross-sectional view of the vehicle powertrain above a central axis showing a torsional damper between the engine and the torque converter.

detailed description

[0027] FIG. 1 illustrates a hybrid electric vehicle 10 that is schematically represented in a parallel hybrid electric drive train. The hybrid electric vehicle is provided with an engine I2 having a rotation output connected to the disconnect clutch 14 of the drive motor I6. The output of the electric motor is connected to the input of the torque converter 18, and the output of the torque converter is connected to the input shaft of the automatic transmission 20. In the conventional manner, the automatic transmission is coupled to the drive wheels 22, 22' by a differential 24. In the schematic, the hybrid electric vehicle 10 is provided with a pair of non-drive wheels, however, alternatively, the transfer case and the second differential can be utilized to actually drive all of the wheels of the vehicle. The engine, disconnect clutch, electric motor, torque converter and automatic transmission are sequentially connected in series as shown in FIG.

[0028] The motor/transmission assembly 26 in the hybrid electric vehicle 1'' schematically illustrated in FIG. 2 reassembles the transmission components while maintaining the same power flow as shown in FIG. The engine 12 is mechanically coupled to the input side above the disconnect clutch 14 by a transmission housing 28 that forms an annular chamber that is large enough to extend around the torque converter 18. The output of the disconnect clutch 14 is coupled to an electric motor 16 which in turn is coupled to the impeller "I" of the torque converter 18. The use of the transmission housing 28 allows the disconnect clutch and motor to be located within the wet side of the automatic transmission housing. The turbine "T" is connected to the output of the torque converter 18, which is connected to the input shaft of the automatic transmission in a conventional manner. The invention can be implemented using a wide variety of automatic transmissions. Preferred embodiments of the transmission described herein are six gear speeds, three planetary gear sets, five clutch designs; alternative transmission configurations with fewer or more speeds and different mechanical configurations can also benefit from this invention.

A more detailed, but simple illustration of the motor/transmission assembly 26 is shown in FIG. The engine has a crankshaft output flange 30 that is bolted to the mounting plate 32 in a conventional manner. The mounting plate 32 is attached to the transmission housing 28 of a diameter sufficient to surround the torque converter and is coupled to the input hub 34 of the disconnect clutch 14, rather than to the housing of the torque converter. The output of the disconnect clutch is fixed to the rotor "R" portion of the motor 16 and, in turn, to the rotor shaft 36. The rotor shaft 36 is coaxially nested within the disconnect clutch input hub 34 and extends to an annular opening in the wall of the transmission housing that defines the wetted region of the transmission. The rotor shaft 36 is coupled to the impeller "I" of the torque converter 18, which in turn drives a turbine T that is coupled to the transmission input shaft 38. Coordinated between the inner diameter of the rotor shaft 36 and the outer circumference of the transmission input shaft 38 is a stator shaft 40 that is fixed relative to the transmission housing and that supports the stator element S located within the torque converter 18.

[0030] Preferably, the housing of the motor/transmission assembly is comprised of a wet outer casing 42 that partially defines a closed wet zone cavity, and a torque converter outer casing 44 that is modified to be secured to the wet outer casing 42 and the engine block 46. The torque converter housing 44 is preferably provided with a rear wall 48 having an annular axial opening 50 on the transmission centerline. The rear wall 48 forms a physical boundary between the wet zone cavity in the transmission housing and the drying cavity. The torque converter 18 and the transmission housing 28 are located in the drying zone as shown. The rear wall 48 cooperates with a disconnect clutch input hub 34 which in turn supports the rotor shaft 36 of the motor and the rotor portion R of the associated motor 16.

The motor/transmission assembly is provided with a pump P for hydraulic fluid oriented in the wet zone of the transmission housing and is driven by the rotor shaft 36. The pump P provides pressurized hydraulic fluid to manipulate clutches and brakes within the transmission driveline and to operate the disconnect clutch and provide cooling to the clutch and motor 16. Similarly, the split clutch and electric motor share a common sump 52 for the transmission fluid and share a common chute 54. The automatic transmission 20 is provided with an output shaft 56. 4a is a cross-sectional side elevational view of the motor/transmission assembly 26. Again, the present invention can use a variety of different transmission gear train configurations and is not limited to the six disclosed speed-shift, three planetary gear set transmissions.

[0032] Referring to the symbolic view of Figure 4b, the preferred embodiment of the multi-speed transmission shown in Figure 4a is more readily understood. The input drive from the engine is fixed to a mounting plate 32 that is coupled to the drive housing 28 of the input hub 34 of the disconnect clutch 14. The output side of the disconnect clutch 14 is coupled to the rotor portion of the electric motor 16, which in turn is coupled to the rotor shaft 36. Coaxially oriented within the rotor shaft 36 is a fixed stator shaft 40 mounted to the transmission housing, and a transmission input shaft 38. The torque converter impeller I drives a torque converter turbine T that is coupled to the transmission input shaft 38. The torque converter 18 further includes a stator S that is attached to the stator shaft 40 via a one-way clutch 56. In a preferred embodiment, the torque converter 18 also has a lockup clutch 58 that locks the turbine to the impeller in a known manner.

[0033] The gear set of the planetary automatic transmission 20 consists of three planetary stars: Planet 1, Planet 2 and Planet 3, which are coaxially aligned and axially spaced as shown. Each planetary gear set has a sun gear, a gear ring, and a series of planet gears supported on the planet carrier. The sun gear, gear ring and planet carrier assembly can be interconnected by a series of five clutches and brakes. For example, in the first gear, clutch A and brake D are engaged as described in the clutch application table of Figure 4c. The transmission input shaft 38 is coupled to the gear ring of the planetary gear set planet 1. The sun gear is fixed and the planet carrier is coupled to the sun gear of the planetary gear set 3 via clutch A. When the clutch D is engaged, the planet carrier of the planetary gear set 3 is fixed, causing the ring gear of the planetary gear set 3 to drive the transmission output shaft. In order to shift to the second gear, the brake D is released and the brake c is engaged at the same time to cause a change in the gear ratio of the transmission. Each transition, either up or down, is accomplished by loosening one clutch or brake and engaging the other. Similarly, the transition from the first reverse gear is accomplished by releasing a single clutch while engaging another clutch.

[0034] The planetary gear sets 2 and 3 share a common planetary element and a common ring gear. The planetary gear set is a conventional, simple planetary gear set, and the planetary gear set 3 is a compound planetary gear set having a pair of intermeshing planets, one of the pair of intermeshing planets engaging the sun gear, one engaging gear ring. In the embodiment depicted in Figure 4b, the composite planetary arrangement allows the third planetary gear set to use a smaller sun gear, resulting in a higher gear reduction ratio. Moreover, the planetary gear set is described merely to illustrate a preferred embodiment, however, the present invention can also be implemented using a wide variety of automatic transmission configurations.

[0035] FIG. 5 is a cross-sectional view showing an alternative drive housing arrangement 62 designed to accommodate a smaller diameter mounting plate 64. The output flange 30 of the crankshaft of the engine is secured to the mounting plate 64 by a series of bolts that pass through a plurality of holes in the mounting plate that are spaced from the center of the mounting plate. The peripheral edge of the mounting plate 64 is provided with a ring gear 66 to cooperate with the pinion of the starter motor. The inner side of the periphery of the mounting plate is a series of holes sized to receive threaded fasteners to connect the transmission housing 62 to the mounting plate 64. In the illustrated embodiment, the drive housing 62 is provided with studs 108 that pass through a set of holes in the mounting plate 64 to receive a nut to securely secure the transmission housing to the mounting plate. The nut can optionally be welded to the mounting plate to receive a bolt that passes through a hole in the mounting plate. In order to reduce torque fluctuations, the mounting plate may optionally also include a dual mass damper (not shown). Unlike conventional automatic transmission vehicles, the torque converter 18 is not bolted to the engine mounting plate, but is free to rotate within the annular cavity defined by the transmission housing 62 and the mounting plate 64. The rear end of the transmission housing forms a tubular transmission housing outlet assembly 68, The assembly is coupled to a disconnect clutch input hub 34. "Back" refers to the direction toward the transmission output shaft 56, which may be the rear of the vehicle in a conventional rear wheel drive front engine vehicle, however, the terms "rear" and "front" are used for simplicity and illustration. the goal of. They do not necessarily refer to the front and rear of the vehicle, as this is not the case if it is installed laterally in a front-wheel drive vehicle. The front side of the torque converter 18 has no bolts typically used to connect to the mounting plate. [0037] Preferably, the transmission housing tubular output hub 68 is internally splined to axially cooperate with a complementary external spline on the split clutch input hub 34. The disconnect clutch 14 has a series of spaced apart plates that are optionally coupled to the input hub 34 and the output hub 70. The split hub annular pistons 72 cooperate within respective cavities formed in the split clutch output hub 70 and are axially changeable between an extended locked position and a retracted position, wherein when a propulsion split clutch piston is received The hydraulic signal of 72 is in the extended locked position and is in the retracted position when the signal is not present. Fixed to the outer circumference of the disconnect clutch output hub 70 is a rotor R. Both the split clutch output hub 70 and the rotor R are mounted and fixed to the rotor shaft 36. The rotor shaft 36 is provided with external splines of a size that cooperate with complementary internal splines on the torque converter input hub 74 of the impeller I. The torque converter 18 also has a stator S mounted on a stator hub 76 and an output turbine T coupled to the turbine output hub 78 by a torsional damper 82 as described in FIG. The turbine output hub 78 is provided with internal splines that cooperate with the transmission input shaft 38. A stator hub 76 is mounted on the stator shaft 40 that is secured to the transmission housing and extends out of the transmission housing. In the illustrated embodiment, the stator is mounted in the center of the one-way clutch in a conventional manner.

[0038] The torque converter 18 and the transmission housing 62 together with four different coaxially arranged components in the transmission and are slid or opened like a conventional torque converter in an automatic transmission during installation, simply The ground has an additional coaxial assembly, namely the tubular output 68 of the transmission housing 62. Therefore, the use of the transmission housing occupies a small additional axial space in the motor/transmission assembly. However, the addition of the disconnect clutch 14 and the electric motor 16 to the transmission takes up some additional axial space within the transmission housing. As shown in Figure 6, the motor is oriented coaxially with a disconnect clutch mounted within the rotor R of the motor. The motor stator S is fixedly secured to the transmission housing by a series of annularly spaced bolts that pass through the stator laminations. The motor rotor R is mounted on the outer circumference of the split clutch output hub 70 supported on the rotor shaft 36.

The rotor shaft 36 is radially positioned by a roller bearing 80 disposed between the rotor shaft 36 and the split input clutch hub 34. The outer diameter of the split clutch input hub is supported by bearings 84 on a wall 48 in the transmission housing. The bearing 84 is designed to have an axial load and a radial load inserted into the rotor split clutch output hub assembly. The split clutch output hub 70 is also axially constrained by thrust bearings 86 and 88. In addition, a ring axle roller bearing 90 is placed between the split clutch output hub 70 and the stator shaft 40 to axially position the rotor shaft 36 and associated disconnect clutch and rotor.

The split clutch output hub 70 is provided with an internal coolant passage 92 that allows the transmission fluid to flow into the rotor R through the split clutch output hub. As the fluid passes through and exits the rotating rotor R, it passes through the coils of the stator S to remove excess heat from the stator coils and associated stator laminations. As shown in FIG. 6, the disconnect clutch output hub 70 is further provided with an output spline 94 for driving the pump P.

[0041] Because the torque converter 18 is no longer fixed to the engine mounting plate, the torque converter must be axially and radially constrained. The torque converter 18 is pivotally supported on the engine mounting plates 32 and 64 of Figures 3 and 5. The engine mounting plates 32, 64 are provided with an axially mounted first bearing assembly 96 that cooperates with a second bearing assembly that mates with the torque converter 18. As shown in Figure 7, the first bearing assembly in the preferred embodiment is provided by a roller bearing 96 supported in a bearing outer ring 98 that is secured to a mounting plate on the transmission centerline. A corresponding second bearing assembly is provided by a stub shaft 100 that is secured to the housing of the torque converter 18. The short shaft provides radial support for the torque converter, while the bearing 96 also provides axial stop for the torque converter in the forward direction. To limit the rearward movement of the torque converter, the torque converter has a rearward facing thrust bearing 102 on the axial centerline inside the casing to engage the end region of the transmission input shaft 38. Of course, alternative configurations can be used, such as placing the stub shaft on the mounting plate and placing the roller bearing on the torque converter housing.

[0042] The motor/transmission assembly 26, as previously described, utilizes a plurality of separate and novel sub-components. Figure 8 is a perspective view of a mounting plate 64 constructed of a disk having a first axially axially aligned bearing assembly, i.e., a roller bearing 96 mounted in a bearing outer race 98. The disk has two circular arrays of mounting holes, one array adjacent the center to connect to the crankshaft of the engine and the other array adjacent the periphery to connect to the transmission housing 28.

[0043] The torque converter 18 described in Figure 9 is also novel. The torque converter housing does not have a conventional mounting stud but has a central axial second bearing assembly, in which case it is provided by the stub shaft 100. Other axial center bearing assemblies may alternatively be used as long as they cooperate with corresponding bearing structures on the mounting plate to withstand radial loads and provide a defined forward stop for torque converter movement. The torque converter has an annular rear portion facing the tubular outlet hub 68 that is coupled to the rotor shaft 36, and a rear portion of the thrust bearing 102 that faces the centerline within the casing as shown in FIG. 7 to abut the transmission input shaft 38. End.

FIG. 10 illustrates a perspective view of the transmission housing 28. The drive housing is an annular assembly having a peripheral structure that is large enough to freely surround the torque converter. The leading edge of the drive housing 28 is provided with a series of spaced apart fasteners 104 to cooperate with the mounting plate 32. The rear end of the drive housing forms a tubular output 68 that preferably has a splined inner diameter to engage a corresponding spline on the split clutch input hub 34. The spaced apart fasteners 104 are a series of welded studs, however, the welded studs can also be used to cooperate with bolts that pass through corresponding holes in the mounting plate.

[0045] FIG. 11 illustrates an alternative transmission housing embodiment 62 of FIG. 5 as previously described. To accommodate a smaller diameter mounting plate and a relatively larger torque converter, the transmission housing is provided with a series of inwardly projecting radial assemblies 1〇6 to support the fasteners. The fasteners shown are provided by studs 108 located on the mounting plate with diameters that are significantly smaller than the diameter of the torque converter. Thus, the inwardly projecting assembly 106 encases the torque converter 18 within a larger annular cavity formed within the transmission housing 62 to produce the transmission housing torque converter subassembly.

[0046] Referring to FIG. 12, the disconnect clutch 14 further includes a barrier ring 110 that is fixedly axially displaced relative to the output hub 70; the balance partition 112 is also fixedly axially displaced relative to the output hub 70; the return spring 114, which contacts the piston 72 and the balancing partition 112 at the other end of the spring; and a sealed hydraulic cylinder 116 wherein the piston is moved by the force and pressure of the spring 114. The hydraulic passage 118 transmits drive pressure from the outlet 120 of the chestnut housing 122 through the axial passage 123 to the cylinder portion 116 located behind the piston 72. When the pressure in the passage 118 is high, the piston 72 moves axially to the left against the force of the spring 114 to urge the friction plate and the diaphragm of the clutch 14 into frictional contact with each other, thereby engaging the clutch 14.

The axial hydraulic passage 124 transfers fluid from the pump housing 122 through the passage 126 to the cylinder portion 116 between the piston 72 and the balance cutoff 112. The hydraulic passage 124 also transfers fluid from the pump housing 122 through the radial passage 92 to the rotor R and stator S of the electric motor 16. Channel 92 is in communication with passage 128 which directs fluid through the width of motor 16 and onto the surface of rotor R. Due to the centrifugal force, the fluid leaving the rotor flows radially outward on opposite axial sides and reaches the surface of the stator S. This fluid, which carries heat out of the motor 16, flows down through the opening 129 (shown in Figure 14) in the outer casing 42 to the sump 52.

[0048] The hydraulic fluid filling the torque converter 18 is transferred from the pump P through the radial passage 130 and the axial passage 132 in the annular space between the stator shaft 40 and the transmission input shaft 38. The front end of the passage 132 communicates with the annular chamber of the torque converter through a radial passage 134, wherein the torque converter is surrounded by a shroud 136 and includes an impeller I, a turbine T, and a stator S. Hydraulic fluid exiting the torque converter 18 is transferred through an axial passage 138 formed in the transmission input shaft 38 and extends along the shaft 140.

[0049] As shown in FIG. 12, the stator S of the electric motor is fixed to the transmission housing 42 by a series of bolts 150, which are composed of an opening 152. Each bolt 150 passes through a hole formed in the stator S, and the threaded shank of each bolt engages a threaded hole formed in the housing 42. Precision dimensional tolerances are determined between the lower surface 153 of the stator S, through the holes in the stator S and the centerline of the bolt 150, and the position of the shaft 140. In this way, the distance between the shaft 140 and the lower surface 153 of the stator S is determined within precise dimensional tolerances to define and maintain a narrow air gap between the stator S and the rotor R of the motor.

[0050] The terminal assembly 154, located on the mounting surface 156 surrounding the opening 152, includes a seat 157 having an electrical terminal 158 that includes at least one coil within the laminated sheet 160 that is electrically coupled to the stator S of the motor. High voltage terminal. Each terminal 158 is connected by a bolt 162 that passes through a plate 164 that is secured to the transmission housing 42 by bolts 166. Each bolt 162 also electrically connects and secures terminal 158 to receptacle 168 that engages conductor 170 that is coupled to stator S. Both the receptacle 168 and the conductor are resiliently bendable in a curved state to complete and maintain their connection to the stator S without substantially changing the distance between the surface 153 and the shaft 140.

[0051] The terminal block assembly 154 is preferably located at an angle relative to the shaft 140 that places the terminal 158 on the side of the transmission housing 42 rather than the higher elevation angle shown in FIG. Preferably, terminal 158 is oriented along axis 140 (although not necessarily parallel to the axis) and the receptacle at the rear of the terminal face, as shown in FIG.

The rotor R of the electric motor 16 is fixed to the output hub 70 to determine an air gap between the reference surface 153 of the stator and the radially outer surface 176 of the rotor.

[0053] As shown in FIG. 14, the outer casing 44 is secured to the transmission housing 42 by a series of bolts 177. The centering plate P of the pump is guided into its correct position, whether radial or axial, due to contact between the surface 178 on the centering plate P of the pump and the guiding surface 180 on the transmission housing 42. Similarly, the pump housing 122 is directed into its proper position due to contact between the surface 182 on the pump centering plate P and the surface 184 on the pump housing 122. At the rear end, the outer surface of the stator shaft 40 contacts the radially inner surface of the pump centering plate P, and at the front end, the outer surface of the stator shaft 40 contacts the radially inner surface of the torque converter input hub 74.

[0054] The axial and radial position of the bearing 84 is determined by its contact with the rear wall 48 of the outer casing 44. The axial and radial position of the clutch input hub 34 is determined by its contact with the bearing 84. The position of the front end of the rotor shaft 36 is determined by its contact with the roller bearing 80, and the position of the rear end of the rotor shaft 36 is determined by its contact with the inner surface of the chestnut housing 122.

[0055] The position of the output hub 70 and the front end of the rotor R is determined by the contact between the outer surface of the rotor shaft 36 and the inner surface of the output hub 70. The axial and radial position of the bearing 190 is determined by its contact with the pump housing 122. The position of the output hub 70 and the rear end of the rotor R is determined by the contact between the bearing 190 and the output hub 70.

In this way, the radial position of the radially outer surface 176 of the rotor R of the motor 16 is positioned such that the air gap extends parallel to the self-shaft 140 and is located at the reference surface 153 of the stator and the radially outer surface 176 of the rotor. A radius of between about 122 mm is preferred.

FIG. 15 shows a torsional damper 196 in a power path between the engine 12 and the transmission housings 28, 62. The engine 12 is coupled to the input of the damper 196 by a crank flange 30 and a series of bolts 108 spaced apart from each other about the shaft 140 connect the output of the damper 196 to the transmission housings 28,62. The damper 196 attenuates torsional vibrations generated by the engine. The peripheral edge of the damper 196 is provided with a ring gear 66 that is engaged by a pinion that is rotationally driven by a starter motor.

[0058] FIG. 15 shows a damper 196 arranged in series with a damper 82 between the engine 12 and the transmission input shaft 38. The presence of a damper 196 in the power system can eliminate the need for a torsional damper 82 that is located in the torque transfer path of the torque converter 18 between the impeller shroud 136 and the turbine hub 78. When the damper 82 is eliminated, the axial dimensions of the torque converter 18 and the transmission housings 28, 62 can be reduced.

[0059] The detailed embodiments of the present invention are disclosed herein as required; however, it is understood that the disclosed embodiments are only examples of the invention, which may be implemented in various different and alternative ways. The figures are not necessarily to scale; some features may be enlarged or reduced to show the details of the particular components. Therefore, the specific structural and functional details disclosed herein are not to be construed as limiting the invention.

[0060] Although the exemplary embodiments are described above, this is not meant to be an exemplification of the various embodiments of the invention. However, the statements used in the specification are for illustrative purposes, and it is understood that various changes may be made without departing from the spirit and scope of the invention. In addition, additional embodiments of the invention may be formed in combination with the features of various embodiments.