Patent Application
20150107950
The present invention relates to a launch device such as torque converters for automotive automatic transmissions. More particularly, the field of the present invention is that of launch devices such as torque converters for automotive automatic transmissions having a lockup clutch and an integral damper that is actuated upon engagement of the lockup clutch.
A torque converter is a type of hydraulic (fluid) drive launch device used to transfer rotating power from a prime mover, such as an internal combustion engine, to a rotating driven load. Virtually all torque converters have a cover shell with a front end for connection with the engine. A rear end of the cover has a series of blades that form a pump or impeller. Engine rotation of the cover causes the impeller to pump the fluid within the torque converter radially outward. Pressurized fluid from the impeller is directed to a turbine. The turbine redirects the fluid radially inward thereby powering an input shaft of an automatic transmission. Virtually all torque converters also have a stator which is interposed between the impeller and turbine so that it can alter the fluid drive flow returning from the turbine to the impeller. The use of the stator can affect torque multiplication between the impeller and the turbine. The power transmission from the impeller to the turbine provides a fluid connection between the same. The fluid drive connection between the turbine and impeller provides torsional damping from vibration that is induced by the periodic changes of velocity of the engine crankshaft due to the reciprocal nature of piston internal combustion engines. However, the fluid drive connection between the impeller and turbine comes at a cost of lower fuel efficiency because there is inherent slippage between the turbine and the impeller.
As the demands for fuel economy have increased, most torque converters have been provided with a lockup clutch. The lockup clutch includes a fluid pressure actuated plate piston. An engine or powertrain controller senses that the vehicle is in a state of operation wherein, for the time being, a shift in transmission gear ratio is not required. Upon this determination, the lockup clutch piston will be fluid pressurized to latch the turbine to a torque converter cover so that the turbine is mechanically rotated by the cover with no slippage in relationship to the impeller. When the lockup occurs, there is a lack of torsional damping due to the lack of the fluid drive connection between the impeller and the turbine. To compensate for this lack of dampening, there has been provided various torsional dampers (often referred to as dampeners). Many of the torsional dampers within torque converters have worked in a principal similar to that of torsional vibrational dampers in general. Typically, the lockup clutch piston or a plate associated therewith and the turbine are torsionally engaged with one another by coil springs captured in axially aligned circumferential slots provided in the piston and turbine. The coil springs provide torsional damping when the piston and turbine move angularly with respect to one another. An example of such a damping arrangement can be found in U.S. Patent Application Publication No. 2009/0151344 to Digler et al.
Because the coil springs are in circumferential spring retainer slots, damping is not as uniform as desired since the springs tend to want to return to their originally manufactured straight axis. Additionally, rotation of the piston and the turbine caused centrifugal force induced bending in the coil spring that hampers uniform damping by causing sliding friction with the spring retainer. The above noted conditions causes hysteresis (an amount of torque required to bring the damper back to zero after loading. It is essentially friction in the system).
It is desirable to provide a damper for the lockup clutch of a launch device such as a torque converter for an automatic transmission with less hysteresis.
To meet the above noted and other manifold desires, a revelation of the present invention is brought forth. The present invention provides a launch device or torque converter for an automotive vehicle with a multiple rate damper for the lockup clutch. The launch device of torque converter of the present invention has a cam ring connected with the lockup clutch piston or turbine that is engaged by a spring loaded rotary member(s) of the torque converter the other one of the turbine to provide multiple rate damping between the lockup clutch piston and the turbine of the torque converter.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.
A torque converter 7 launching device according to the present invention is provided. The torque converter 7 includes a front cover 10. The front cover 10 along a forward end 12 is torsionally connected with the crank shaft of the prime mover. The prime mover is typically a reciprocating piston internal combustion engine. Due to the inherent design of reciprocating piston engines, there exists a vibratory oscillation about the mean velocity of the engine. The torque converter 7 front cover 10, at a rear end 14 is weldably connected to a rear cover 16. The rear cover 16 and front cover 10 define a first control volume 18. Fixably connected with the rear cover 16 is an impeller 22 formed by a plurality of impeller blades 23. Positioned within the control volume 18 is a turbine 24. The turbine 24 includes a series of blades 26 connected with a shell 28. The shell 28 is weldably connected with a two-part hub 30 including a plate 32 and an inner hub 34 that is splined to the input shaft 36 of an automotive transmission. Positioned between the impeller 22 and the turbine blade 26 is a stator 38. The stator 38 redirects flow coming from the turbine 24 back to the impeller 22. Slidably sealably mounted on the inner hub 34 is a plate piston 42. The plate piston 42 along its outer edge has an engagement surface 44. The engagement surface 44 or the interior of the front cover 10 or both may have friction materials 46 bonded thereto.
Fixably connected to the lockup clutch piston 42 by rivets or other suitable connective method, is a cam plate ring 50. The cam plate ring 50 has an interior cam surface 52. Engaged with the interior cam surface 52 of the cam ring 50 is a rotary member 56. In many applications, it is preferable to have multiple rotary members 56, preferably geometrically equally spaced from one another. In most applications, at least three rotary members are preferable. Radially biasing the rotary member 56 against the cam surface 52 is a coil spring 58.
In operation, the front cover 10 is torsionally connected with the crank shaft of an automotive vehicle. The rotation of the front cover 10 in turn also rotates the rear cover 16 causing the blades 23 of the impeller 22 to rotate. Rotation of the impeller 22 causes the fluid to go radially outward turning it into the blades 26 of the turbine 24 thereby causing rotation of the hub 30 and transmission shaft 36. A stator 38 is utilized to redirect the fluid flowing from the turbine 24 back to the impeller 22 to dictate a desired torque ratio between the impeller 22 and turbine 24. When it is desired to lockup the turbine 24 with the front cover 10 a pump (not shown) is utilized to pressurize the control volume 18 causing the piston 42 to be urged forward causing its frictional engagement portion 44 to latch to the front cover 10 via the friction material 46. The turbine 24 is now locked to the front cover 10 and impeller 22. The rotary members or rollers 56 are urged radially outward by the spring 58 so that it engages with the cam surface 52.
To dampen the torsional vibration received by the primary mover, the cam surface when laid out in a graph of damper torque versus displacement between the cam ring 50 and the rotary axis 64 of the rotary member (essentially a function of the relative angular displacement between the cam ring 58 and the hub 30) approaches that of curves 67, 68 or 69 of
If desired, the torque converter 7 of the present invention can have multiple rate dampening for lockup clutch similar to that of prior art torque converters having a damper torque versus travel degree curve as shown in
Referring to
The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.
