Abstract:
A pump assembly for a torque converter including a shell arranged to receive a plurality of blades for the pump, a hub arranged to interface with a transmission, and a resilient member located axially between an annular portion of the shell and annular portion of the hub. In a preferred embodiment, the resilient member is an O-ring.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Application No. 60/904,010, filed Feb. 28, 2007, which application is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to improvements in apparatus for transmitting force. The force can be between a rotary driving unit (such as the engine of a motor vehicle) and a rotary driven unit (such as the variable-speed transmission in the motor vehicle), or the force can be transmitted within a rotary driving unit (such as the transmission of a motor vehicle). In particular, the invention relates to a radially compliant pump hub. 
     BACKGROUND OF THE INVENTION 
       FIG. 1  illustrates a general block diagram showing the relationship of the engine  7 , torque converter  10 , transmission  8 , and differential/axle assembly  9  in a typical vehicle. It is well known that a torque converter is used to transmit torque from an engine to a transmission of a motor vehicle. 
     The three main components of the torque converter are the pump  37 , turbine  38 , and stator  39 . The torque converter becomes a sealed chamber when the pump is welded to cover  11 . The cover is connected to flexplate  41  which is, in turn, bolted to crankshaft  42  of engine  7 . The cover can be connected to the flexplate using lugs or studs welded to the cover. The welded connection between the pump and cover transmits engine torque to the pump. Therefore, the pump always rotates at engine speed. The function of the pump is to use this rotational motion to propel the fluid radially outward and axially towards the turbine. Therefore, the pump is a centrifugal pump propelling fluid from a small radial inlet to a large radial outlet, increasing the energy in the fluid. Pressure to engage transmission clutches and the torque converter clutch is supplied by an additional pump in the transmission that is driven by the pump hub. 
     In torque converter  10  a fluid circuit is created by the pump (sometimes called an impeller), the turbine, and the stator (sometimes called a reactor). The fluid circuit allows the engine to continue rotating when the vehicle is stopped, and accelerate the vehicle when desired by a driver. The torque converter supplements engine torque through torque ratio, similar to a gear reduction. Torque ratio is the ratio of output torque to input torque. Torque ratio is highest at low or no turbine rotational speed (also called stall). Stall torque ratios are typically within a range of 1.8-2.2. This means that the output torque of the torque converter is 1.8-2.2 times greater than the input torque. Output speed, however, is much lower than input speed, because the turbine is connected to the output and it is not rotating, but the input is rotating at engine speed. 
     Turbine  38  uses the fluid energy it receives from pump  37  to propel the vehicle. Turbine shell  22  is connected to turbine hub  19 . Turbine hub  19  uses a spline connection to transmit turbine torque to transmission input shaft  43 . The input shaft is connected to the wheels of the vehicle through gears and shafts in transmission  8  and axle differential  9 . The force of the fluid impacting the turbine blades is output from the turbine as torque. Axial thrust bearings  31  support the components from axial forces imparted by the fluid. When output torque is sufficient to overcome the inertia of the vehicle at rest, the vehicle begins to move. 
     After the fluid energy is converted to torque by the turbine, there is still some energy left in the fluid. The fluid exiting from small radial outlet  44  would ordinarily enter the pump in such a manner as to oppose the rotation of the pump. Stator  39  is used to redirect the fluid to help accelerate the pump, thereby increasing torque ratio. Stator  39  is connected to stator shaft  45  through one-way clutch  46 . The stator shaft is connected to transmission housing  47  and does not rotate. One-way clutch  46  prevents stator  39  from rotating at low speed ratios (where the pump is spinning faster than the turbine). Fluid entering stator  39  from turbine outlet  44  is turned by stator blades  48  to enter pump  37  in the direction of rotation. 
     The blade inlet and exit angles, the pump and turbine shell shapes, and the overall diameter of the torque converter influence its performance. Design parameters include the torque ratio, efficiency, and ability of the torque converter to absorb engine torque without allowing the engine to “run away.” This occurs if the torque converter is too small and the pump can&#39;t slow the engine. 
     At low speed ratios, the torque converter works well to allow the engine to rotate while the vehicle is stationary, and to supplement engine torque for increased performance. At speed ratios less than 1, the torque converter is less than 100% efficient. The torque ratio of the torque converter gradually reduces from a high of about 1.8 to 2.2, to a torque ratio of about 1 as the turbine rotational speed approaches the pump rotational speed. The speed ratio when the torque ratio reaches 1 is called the coupling point. At this point, the fluid entering the stator no longer needs redirected, and the one way clutch in the stator allows it to rotate in the same direction as the pump and turbine. Because the stator is not redirecting the fluid, torque output from the torque converter is the same as torque input. The entire fluid circuit will rotate as a unit. 
     Peak torque converter efficiency is limited to 92-93% based on losses in the fluid. Therefore torque converter clutch  49  is employed to mechanically connect the torque converter input to the output, improving efficiency to 100%. Clutch piston plate  17  is hydraulically applied when commanded by the transmission controller. Piston plate  17  is sealed to turbine hub  19  at its inner diameter by o-ring  18  and to cover  11  at its outer diameter by friction material ring  51 . These seals create a pressure chamber and force piston plate  17  into engagement with cover  11 . This mechanical connection bypasses the torque converter fluid circuit. 
     The mechanical connection of torque converter clutch  49  transmits many more engine torsional fluctuations to the drivetrain. As the drivetrain is basically a spring-mass system, torsional fluctuations from the engine can excite natural frequencies of the system. A damper is employed to shift the drivetrain natural frequencies out of the driving range. The damper includes springs  15  in series with engine  7  and transmission  8  to lower the effective spring rate of the system, thereby lowering the natural frequency. 
     Torque converter clutch  49  generally comprises four components: piston plate  17 , cover plates  12  and  16 , springs  15 , and flange  13 . Cover plates  12  and  16  transmit torque from piston plate  17  to compression springs  15 . Cover plate wings  52  are formed around springs  15  for axial retention. Torque from piston plate  17  is transmitted to cover plates  12  and  16  through a riveted connection. Cover plates  12  and  16  impart torque to compression springs  15  by contact with an edge of a spring window. Both cover plates work in combination to support the spring on both sides of the spring center axis. Spring force is transmitted to flange  13  by contact with a flange spring window edge. Sometimes the flange also has a rotational tab or slot which engages a portion of the cover plate to prevent over-compression of the springs during high torque events. Torque from flange  13  is transmitted to turbine hub  19  and into transmission input shaft  43 . 
     Energy absorption can be accomplished through friction, sometimes called hysteresis, if desired. Hysteresis includes friction from windup and unwinding of the damper plates, so it is twice the actual friction torque. The hysteresis package generally consists of diaphragm (or Belleville) spring  14  which is placed between flange  13  and one of cover plates  16  to urge flange  13  into contact with the other cover plate  12 . By controlling the amount of force exerted by diaphragm spring  14 , the amount of friction torque can also be controlled. Typical hysteresis values are in the range of 10-30 Nm. 
     Pump hub  35  is arranged to interface with the transmission. Normally, pump hub  35  is rigidly attached to pump shell  34 , i.e., by welding. Bushing  36  allows differing rotational speeds between torque converter  10  and stator shaft  47 . In some designs, bushing  36  also centers pump side of torque converter  10  relative to the transmission (not shown). Flexplate  53  is required to compensate for misalignment between the engine and transmission because torque converter  10  is centered on engine side by cover pilot  54  and on transmission side by pump hub  35 . 
     Pump hub  35  is arranged to transmit torque to the transmission pump (not shown). Pump hub  35  may use features including flats, notches, or tabs to transmit torque. These features must be robustly designed to prevent failure caused by torque spikes between the engine and transmission pump because pump hub  35  is rigidly attached to pump shell  34 . 
     Thus, there is a long-felt need for a torque converter pump incorporating a hub connection method that compensates for misalignment between the engine and transmission. Furthermore, there is a need for a torque converter pump incorporating a non-rigid hub connection method to limit torque spikes transmitted to the torque transmission features of the pump hub. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention broadly comprises a pump assembly for a torque converter including a shell arranged to receive a plurality of blades for the pump, a hub arranged to interface with a transmission, and a resilient member located axially between an annular portion of the shell and annular portion of the hub. In a preferred embodiment, the resilient member is an O-ring. 
     In a preferred embodiment, the pump hub includes means for rotating a hydraulic pump in the transmission. In one embodiment, the means is a notch or a flattened portion of the hub. 
     In a preferred embodiment, the pump includes a means for compressing the resilient member. In another preferred embodiment, the resilient member is an O-ring and the compressing means is a speed nut. In some aspects, the pump shell, pump hub, or both includes a circumferential groove for receiving the O-ring. 
     The invention also broadly comprises a torque converter including a pump shell arranged to receive a plurality of blades, a hub arranged to interface with a transmission, and a frictional connection between the shell and the hub. In a preferred embodiment, the torque converter also includes a cover connected to the pump shell and the torque capacity of the connection between the pump shell and the cover is greater than the torque capacity of the frictional connection. In another preferred embodiment, the hub is radially displaceable in relation to the pump shell. 
     The invention also broadly comprises a method for assembling a pump hub to a pump shell comprising positioning a resilient member between the pump hub and the pump shell and compressing the resilient member between the pump hub and the pump shell. In a preferred embodiment, compressing the resilient member between the pump hub and the pump shell includes retaining the hub with respect to the shell. 
     These and other objects and advantages of the present invention will be readily appreciable from the following description of preferred embodiments of the invention and from the accompanying drawings and claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The nature and mode of 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: 
         FIG. 1  is a general block diagram illustration of power flow in a motor vehicle, intended to help explain the relationship and function of a torque converter in the drive train thereof; 
         FIG. 2  is a cross-sectional view of a prior art torque converter, shown secured to an engine of a motor vehicle; 
         FIG. 3  is a left view of the torque converter shown in  FIG. 2 , taken generally along line  3 - 3  in  FIG. 2 ; 
         FIG. 4  is a cross-sectional view of the torque converter shown in  FIGS. 2 and 3 , taken generally along line  4 - 4  in  FIG. 3 ; 
         FIG. 5  is a first exploded view of the torque converter shown in  FIG. 2 , as shown from the perspective of one viewing the exploded torque converter from the left; 
         FIG. 6  is a second exploded view of the torque converter shown in  FIG. 2 , as shown from the perspective of one viewing the exploded torque converter from the right; 
         FIG. 7A  is a perspective view of a cylindrical coordinate system demonstrating spatial terminology used in the present application; 
         FIG. 7B  is a perspective view of an object in the cylindrical coordinate system of  FIG. 7A  demonstrating spatial terminology used in the present application; 
         FIG. 8  is a front view of a present invention torque converter pump shown with the blades removed for clarity; 
         FIG. 9  is a sectioned perspective view of the torque converter pump shown in  FIG. 8 ; 
         FIG. 10  is a section view of the torque converter pump shown in  FIG. 8  taken generally along line  10 - 10  in  FIG. 8 ; and, 
         FIG. 11  is a detail view of encircled region  11  in  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     At the outset, it should be appreciated that like drawing numbers on different drawing views identify identical, or functionally similar, structural elements of the invention. While the present invention is described with respect to what is presently considered to be the preferred aspects, it is to be understood that the invention as claimed is not limited to the disclosed aspects. 
     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. 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. 
       FIG. 7A  is a perspective view of cylindrical coordinate system  80  demonstrating spatial terminology used in the present application. The present invention is at least partially described within the context of a cylindrical coordinate system. System  80  has a longitudinal axis  81 , used as the reference for the directional and spatial terms that follow. The adjectives “axial,” “radial,” and “circumferential” are with respect to an orientation parallel to axis  81 , radius  82  (which is orthogonal to axis  81 ), and circumference  83 , respectively. The adjectives “axial,” “radial” and “circumferential” also refer to orientation parallel to respective planes. To clarify the disposition of the various planes, objects  84 ,  85 , and  86  are used. Surface  87  of object  84  forms an axial plane. That is, axis  81  forms a line along the surface. Surface  88  of object  85  forms a radial plane. That is, radius  82  forms a line along the surface. Surface  89  of object  86  forms a circumferential plane. That is, circumference  83  forms a line along the surface. As a further example, axial movement or disposition is parallel to axis  81 , radial movement or disposition is parallel to radius  82 , and circumferential movement or disposition is parallel to circumference  83 . Rotation is with respect to axis  81 . 
     The adverbs “axially,” “radially,” and “circumferentially” are used with respect to an orientation parallel to axis  81 , radius  82 , or circumference  83 , respectively. The adverbs “axially,” “radially,” and “circumferentially” also are regarding orientation parallel to respective planes. 
       FIG. 7B  is a perspective view of object  90  in cylindrical coordinate system  80  of  FIG. 7A  demonstrating spatial terminology used in the present application. Cylindrical object  90  is representative of a cylindrical object in a cylindrical coordinate system and is not intended to limit the present invention is any manner. Object  90  includes axial surface  91 , radial surface  92 , and circumferential surface  93 . Surface  91  is part of an axial plane, surface  92  is part of a radial plane, and surface  93  is part of a circumferential plane. 
       FIG. 8  is a front view of a torque converter pump of the present invention shown with the blades removed for clarity.  FIG. 9  is a sectioned perspective view of the torque converter pump shown in  FIG. 8 .  FIG. 10  is a section view of the torque converter pump shown in  FIG. 8  taken generally along line  10 - 10  in  FIG. 8 .  FIG. 11  is a detail view of encircled region  11  in  FIG. 10 . The following should be viewed in light of  FIGS. 8-11 . 
     Torque converter pump  100  includes shell  102  and hub assembly  104 . Shell  102  is attached to and receives torque from a torque converter cover (not shown) as described supra. Shell  102  includes indent arrangements  106 ,  108 , and  110  for receiving pump blades (not shown). 
     Hub assembly  104  includes pump hub  112  and compressible resilient element  114 . By compressible resilient, we mean that the element can be compressed, but will exert a counteracting, resilient, force against the compression. Pump hub  112  includes cylindrical region  116  and annular region  118 . In a preferred embodiment, cylindrical region  116  and annular region  118  are integrated into a single component. In another embodiment, regions  116  and  118  are individual components and are connected using any means known in the art (i.e., welding or brazing). In a preferred embodiment, pump hub  112  is a deep drawn stamping formed of low carbon steel. Pump hub  112  further includes means for interfacing with a hydraulic pump in a transmission (not shown). Interfacing means may be any means known in the art. In a preferred embodiment, interfacing means are slots, notches, or flattened portions (not shown) of hub  112 . 
     Shell  102  further includes hole  120 . Diameter  122  of hole  120  is larger than diameter  124  of cylindrical portion  116  of pump hub  112 . Therefore, cylindrical portion  116  of pump hub  112  can pass through shell  102 . Thus, hub  112  is radially displaceable with respect to the shell. Radial clearance between hole  120  and pump hub  112  compensates for misalignment between an engine (not shown) and a transmission (not shown). Diameter  126  of annular portion  118  is larger than diameter  122  of hole  120 , preventing annular portion  126  from passing through hold  120  in shell  102 . 
     Resilient element  114  is positioned between shell  102  and annular portion  118  of pump hub  112 . Resilient element  114  can be any applicable element known in the art. In a preferred embodiment, resilient element  114  takes the form of a ring with a circular cross section. In another preferred embodiment, resilient element  114  is an O-ring composed of a commercially available fluorocarbon (i.e. Viton® brand fluorocarbon). Resilient element  114  may be radially located by any means known in the art. In a preferred embodiment, circumferential groove  130  in shell  102  locates resilient element  114 . In another embodiment (not shown), resilient element  114  is located by a circumferential groove in or axial extension of pump hub  112 . 
     Retaining element  132  pulls portion  118  towards shell  102 , thereby compressing resilient element  114 . In a preferred embodiment, retaining element  132  is a cone-shaped ring. That is, an inner diameter of the element is cone shaped. The cone shape causes the element to lock onto portion  116  once element  132  is slid onto portion  116 , preventing the portion of element  132  in contact with portion  116  from sliding in direction  133 . Thus, element  132  reacts against shell  102  and the reaction force is transferred to hub  104  in direction  133  by the locked connection of element  132  with portion  116 . In another preferred embodiment (not shown), retaining element  132  is a speed nut. Though a retaining ring is shown, any retaining method known in the art (i.e., tabs or clips) may be employed to maintain compression on resilient element  114 . 
     Compression of resilient element  114  between shell  102  and hub  112  creates a fluid-tight seal, preventing oil leakage. Oil pressure inside the torque converter assembly from the transmission pump or centrifugal forces further compresses resilient element  114  by forcing portion  118  toward the shell. Therefore, increased oil pressure further prevents oil leakage by applying additional compressive force to resilient element  128 . 
     Compression of resilient element  114  enables torque transmission from shell  102  to hub  112 . The amount of compression introduced by retaining means  132  is determined by the normal force required at the ring diameter to transmit torque sufficient to drive the transmission pump. Typically, operation of the transmission pump requires minimal torque (about 10 Nm), so material limits for compression of resilient element  114  can be adhered to while still driving transmission pump. Transmission of torque in this manner creates a slip-clutch that prevents torque spikes from damaging pump hub  112 . That is, for torque forces up to the minimal torque noted above, the combination of hub  112  and element  114  transfers torque between the shell and the pump. For torque forces greater than the minimal torque noted above, the pump hub slips with respect to element  114  and the shell, preventing the transmission of these potentially damaging forces. 
     Engine and transmission misalignment and torque spikes from the transmission pump are compensated for by the inventive design. Therefore, an inventive pump hub may be thinner and less robust than typical hubs, advantageously reducing material costs and simplifying fabrication operations. In a preferred embodiment, hub  112  has no further processing after forming, thereby reducing manufacturing costs. 
     Thus, it is seen that the objects of the present invention are efficiently obtained, although modifications and changes to the invention should be readily apparent to those having ordinary skill in the art, which modifications are intended to be within the spirit and scope of the invention as claimed. It also is understood that the foregoing description is illustrative of the present invention and should not be considered as limiting. Therefore, other embodiments of the present invention are possible without departing from the spirit and scope of the present invention.