Patent Publication Number: US-2021180669-A1

Title: Attachment of engine-connecting lug to torque converter cover

Description:
TECHNICAL FIELD 
     The present disclosure relates to torque converters and more specifically to connections between the torque converter and an engine. 
     BACKGROUND 
     Automatic transmissions may include a torque converter for coupling a transmission input shaft to a crankshaft of an engine. The torque converter may include an impeller fixed to the crankshaft, a turbine fixed to the input shaft, and a stator disposed between the impeller and the turbine. The torque converter may also include a bypass clutch to mechanically couple the transmission input shaft to the case of the torque converter, which is fixed to the crankshaft. 
     SUMMARY 
     According to one embodiment, a torque converter includes an impeller and a cover non-rotatably fixed to the impeller. The cover has opposing inner and outer surfaces and a through hole extending from the inner surface to the outer surface. A lug has a collar adjacent the outer surface, a shank extending from a first side of the collar, and a stem extending from a second side of the collar. The stem is disposed in the hole and attached to the cover by a connection. The connection may be a weld. 
     According to another embodiment, a torque converter includes an impeller having a shell and impeller blades fixed to an inside surface of the shell. The torque converter further includes a turbine configured to fluidly couple with the impeller. A cover is non-rotatably fixed to the impeller. The cover has opposing inner and outer surfaces and defines a plurality of circumferentially arranged through holes having sidewalls extending from the inner surface to the outer surface. A plurality of lugs are configured to connect the cover to a flex plate. Each of the lugs has a shank and a stem. The stems are disposed in corresponding ones of the holes such that the shanks extend from the outer surface of the cover. The stems are attached to the cover by coalescence between the stems and the sidewalls. 
     According to yet another embodiment, a method includes providing a cover having opposing inner and outer surfaces and a through hole extending from the inner surface to the outer surface. The method further includes installing a lug on the cover by inserting a stem of the lug into the hole such that a shank of the lug projects from the outer surface. The method also includes welding the stem to a sidewall of the hole such that a weld completely encircles the stem to attach the lug to the cover and seal the hole. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of a torque converter. 
         FIG. 2  is a flow chart illustrating a method of assembling a torque converter. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present disclosure are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and other embodiments can take various and alternative forms. The figures are not necessarily to scale; some features could be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the embodiments. As those of ordinary skill in the art will understand, various features illustrated and described with reference to any one of the figures can be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. Various combinations and modifications of the features consistent with the teachings of this disclosure, however, could be desired for particular applications or implementations. 
     Directional terms used herein are made with reference to the views and orientations shown in the exemplary figures. A central axis is shown in the figures and described below. Terms such as “outer” and “inner” are relative to the central axis. For example, an “outer” surface means that the surfaces faces away from the central axis, or is outboard of another “inner” surface. Terms such as “radial,” “diameter,” “circumference,” etc. also are relative to the central axis. The terms “front,” “rear,” “upper” and “lower” designate directions in the drawings to which reference is made. 
     Referring to  FIG. 1 , a torque converter  20  may be used in a vehicle to couple an automatic transmission to a powerplant, e.g., an engine. For example, the torque converter  20  includes a cover  22  non-rotationally fixed to a crankshaft of the engine. Components that are non-rotationally fixed rotate in unison. An impeller  24  is fixed to the cover  22  and rotates with the crankshaft. The impeller  24  may include a shell  25  and blades  27 . The shell  25  is attached to the cover  22  and forms the back portion of the outer housing of the torque converter  20 . A turbine  26  is disposed adjacent to the impeller  24  within a hydrodynamic chamber  38  of the torque converter  20 . The turbine  26  is attached to a turbine hub  34  that is connected, e.g., splined, to a transmission input shaft that supplies power to the transmission. 
     A stator  28  is coupled to a stator shaft (not shown) by a one-way clutch  32 . The stator shaft is fixed to a front support of the transmission and is stationary relative to the torque converter  20 . When the transmission input shaft is stationary or rotating slowly compared to the crankshaft, the one-way clutch  32  holds the stator  28  stationary. Rotation of the impeller  24  forces fluid to move between the impeller  24 , the turbine  26 , and the stator  28 . The fluid exerts a hydrodynamic torque on the turbine  26 . The stator  28  provides a reaction force causing the torque on the turbine  26  to be greater than the torque on the impeller  24 . When the speed of the turbine  26  approaches that of the impeller  24 , fluid tends to flow around the centerline of the torque converter, causing the one-way clutch  32  to overrun. 
     The torque converter  20  may include a bypass clutch  36  that mechanically connects the turbine  26  to the cover  22  to bypass the hydrodynamic power flow path of the torque converter  20 . The bypass clutch  36  is often engaged during cruise to improve fuel efficiency. The bypass clutch  36  may include a clutch disc  66  operated by a clutch piston  60 . The clutch disc  66  may include at least one friction material  70  disposed thereon. The clutch disc  66  is sandwiched between the clutch piston  60  and the cover  22 . The clutch  36  is engaged by moving the clutch piston  60  towards the cover  22  to frictionally lock the clutch disc  66  to the cover  22 . The turbine  26  is fixed to the clutch disc  66  by a damper  78 . Thus, the turbine  26  is fixed to the cover  22  when the bypass clutch  36  is fully engaged to bypass the hydrodynamic power flow path and instead mechanically couple the engine to the transmission. Other bypass clutch designs may be used in the torque converter  20 . 
     The clutch piston  60  may be hydraulically actuated by supplying fluid, e.g., oil, to an apply chamber  62  or a compensation chamber  64 . The apply chamber  62  and the compensation chamber  64  may be fluidly isolated from the hydrodynamic chamber  38  and from each other. Two chambers may be considered to be fluidly isolated if they are capable of having meaningfully different pressures. The torque converter  20  includes components that cooperate to define the apply chamber  62  and the compensation chamber  64 . 
     The cover  22  defines a circular cutout  80  that seats on a ledge of a cover pilot  82 . The cover  22  may be joined to the cover pilot  82  by welding such as laser welding. The cover pilot  82 , inter alia, supports the turbine hub  34  and may define fluid passageways for operation of the bypass clutch  36  (if provided). 
     The cover  22  is connected to the crankshaft of the engine via a flywheel or the illustrated flex plate  90 . The flex plate  90  is connected to the cover  22  via a plurality of fastener connections  92 . In the illustrated embodiment, the cover  22  includes a plurality of lugs  94  that are inserted through holes  96  defined in the flex plate  90 . The diameters of the holes may substantially equal to diameters of the lugs  94 , albeit slightly larger to provide clearance for insertion. The cover  22  is connected to the flex plate  90  by inserting the lugs  94  through the holes  96  and securing fasteners  100 , e.g., nuts, on the lugs  94 . 
     The cover  22  may be formed as a stamping. Holes  102  are defined through a front face  108  of the cover  22 . The holes  102  are completely through the cover  22  and extend from the interior surface  104  to the exterior surface  106 . The holes  102  may be circular to match the circular lugs  94 . The lugs  94  and the holes  96 ,  102 , however, may include other cross-sectional shapes in other embodiments. The holes  102  are arranged in a circumferential array on the front face  108 . The holes  102  may have equal angular spacing relative to each other and may lie on a common circle. For example, the cover  22  may define four holes equally spaced at 90 degrees. The number of holes, and by extension, the number of lugs, may vary based on the strength requirements of the application. A range of four to six lugs/holes is suitable for most applications. 
     Each lug  94  may include a collar  110 , a shank  112  extending from a first side  113  of the collar  110 , and a stem  114  extending from a second side  116  of the collar  110 . The shank  112  is designed to connect with the flex plate  90 , e.g., be received within the holes  96  of the flex plate and secure thereto, and the stem  114  is designed to be connected to the cover  22 . The lug  94  may be cylindrical with the collar  110  having a larger diameter than the shank  112 , the stem  114 , and the hole  102 . The shank  112  may be longer than the stem  114 . In some embodiments, the collar  110  may not be present, and the flex plate is disposed against the cover  22 . 
     The lugs  94  may be connected to the cover  22  by inserting the stems  114  into the holes  102  and then welding the lugs  94  to the cover  22 . When installed, the second sides  116  of the collars  110  are adjacent the exterior surface  106 . The stems  114  may have a length that is equal to the thickness of the front face  108  or may be longer or short than the thickness in other embodiments. In one or more embodiment, the lugs  94  are laser welded to the cover  22 . Each laser weld creates coalescence between the sidewall  109  of the hole  102  and the stem  114 . The welds may completely encircle the stems  114  to seal the holes  102  and prevent fluid within the torque converter  20  from leaking. 
     Described below are example methods of assembling a torque converter using CD welding. Referring to the flow chart of  FIG. 2  and  FIG. 1 , a method  200  of assembling a torque converter includes forming a cover at operation  202 . For easy of description, the method will be described in conjunction with the illustrated embodiment, but the method is not limited thereto. The cover  22  may be formed by a stamping operation. The stamping process may be performed in one or more steps. Once the cover  22  is stamped, one or more secondary operations may be performed. For example, the holes  96  may be formed through the front face  108 . The holes  102  may be formed by drilling, punching, and the like at operation  204 . In some embodiment, the holes  96  may be formed during the stamping operation  202 . At operation  206 , the lugs  94  are installed on the cover by inserting the stems  114  of the lugs into the holes  102  such that the shanks  112  of the lug project from the outer surface of the cover  22 . The collars  110  may be disposed tightly against the exterior surface  106  of the cover  22 . Once the lugs  94  are installed, a welding tool, such as a laser welder or a metal inert gas (MIG) welder, welds the stems  114  of the lugs to the cover  22 . The welding tool may be applied around the collar  110 . In the case of a laser welder, heat from the laser will melt the stem  114  and the sidewall of the hole  102  to form coalescence. The laser welder may be rotated completely around the lug so that the weld encircles the stem  114  to seal the hole  102  and inhibit leaking. In the case of MIG welding, the welding tool is applied on the back side of the front face  108  and weld material is flowed towards the collar  110 . 
     After the lugs  94  are welded, the remaining components, e.g., impeller, turbine, stator, bypass clutch, etc., of the torque converter  20  may be assembled to form a completed torque converter assembly at operation  210 . During later installation of the torque converter to the engine, the lugs will be inserted through holes of the flex plate and a retainer, such as a nut, will be driven down onto the studs to connect the torque converter to the crankshaft the engine. 
     The above-discussed method steps are not an exhaustive list of all steps for fully assembling a torque converter and instead explain a representative basis for employing internally welded lugs used for connecting the cover to the flex plate. While the method steps are described in a particular sequence, the steps may be performed in other sequences and some steps may be omitted in some embodiments. 
     While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the specification are words of description rather than limitation, and it is understood that various changes can be made without departing from the spirit and scope of the disclosure. As previously described, the features of various embodiments can be combined to form further embodiments of the invention that may not be explicitly described or illustrated. While various embodiments could have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, those of ordinary skill in the art recognize that one or more features or characteristics can be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. These attributes can include, but are not limited to cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. As such, to the extent any embodiments are described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics, these embodiments are not outside the scope of the disclosure and can be desirable for particular applications. 
     The following is a list of reference numbers shown in the Figures. However, it should be understood that the use of these terms is for illustrative purposes only with respect to one embodiment. And, use of reference numbers correlating a certain term that is both illustrated in the Figures and present in the claims is not intended to limit the claims to only cover the illustrated embodiment. 
     PARTS LIST 
     
         
         
           
               20  torque converter 
               22  cover 
               24  impeller 
               25  shell 
               26  turbine 
               27  blades 
               28  stator 
               32  one-way clutch 
               34  turbine hub 
               36  bypass clutch 
               38  hydrodynamic chamber 
               60  clutch piston 
               62  apply chamber 
               64  compensation chamber 
               66  clutch disc 
               70  friction material 
               78  damper 
               80  circular cutout 
               82  cover pilot 
               90  flex plate 
               92  fastener connections 
               94  lugs 
               96  holes 
               100  fasteners 
               102  holes 
               104  interior surface 
               106  exterior surface 
               108  front face 
               109  sidewall 
               110  collar 
               112  shank 
               113  first side 
               114  stem 
               116  second side