Torque converter assemblies have an end cover which is welded to an impeller so as to close the torque converter assembly which is comprised of the impeller, a turbine and a stator disposed in toroidal flow relation, and a torque converter clutch which is disposed to frictionally engage the end cover.
The end covers of the known torque converters are formed by stamping a flat sheet metal component into an end cover shape wherein a central pilot is formed, a circulator strengthening rib area is formed, and the outer periphery is bent away from the pilot diameter to form an outer annular rim portion.
The lugs for connecting the torque converter to an engine are welded onto the stamping, after which the lugs and the stamping are machined on both sides. The dies for creating or manufacturing the stamping require high level investment as well as a very long lead time for replacement parts. Thus, the tooling costs for the torque converter cover are quite extensive.
The end cover is welded to the impeller or pump assembly to thereby form a pressure vessel for the torque converter. Currently, the cover is welded to the impeller by using either electron beam welding, mig welding or most recently, laser welding. Each of these welding processes has its own particular set of undesirable characteristics and all make use of a filler material in the form of welding wire which contributes to sediment within the transmission assembly. Mig welding is the slowest and least clean of the processes and adds a significant amount of process time and sediment. Electron beam welding requires high maintenance and capital investment welding equipment as does laser welding.
When the cover has been welded to the impeller, it is then necessary to provide for balancing the torque converter assembly. The three internal components, that is, the impeller, turbine and stator, are dynamically balanced prior to being assembled within the pressure vessel. After final assembly, however, it becomes necessary to again dynamically balance the entire torque converter assembly. The dynamic balance of the assembly is accomplished by fixing the internal components at one position and determining the imbalance by rotating the assembly on a conventional balancing machine.
The internal components, that is, the turbine clutch assembly and stator, are rotated 180 degrees and another balance measurement is taken. These readings are added vectorially to determine the true balance of the system and an appropriate weight is welded to the exterior of the cover. In theory, this yields an dynamically balanced torque converter assembly.