Power transfer device

#The present invention relates to devices for transferring power from a rotating input shaft to an output shaft. In particular, the present invention relates to torque converters, automatic gearboxes, and power transfer cases which employ clutches for effecting the transfer of power.

#Over the past several years, automotive manufacturers have been forced to produce automobiles which are more fuel efficient and produce less harmful emissions. The vast majority of improvements in the areas have been with fuel delivery systems, emission control systems and vehicle aerodynamics. However, torque converters, automatic gearboxes and power transfer cases are other, often overlooked, sources of inefficiency and harmful emissions.

#Conventional torque converters consist of an impeller coupled to a rotating input shaft, a turbine coupled to an output shaft, and a stator in communication with the impeller and the turbine. As the impeller blades rotate, the impeller directs hydraulic fluid between the stator and the turbine, urging the stator to rotate in the direction opposite to that of the impeller and the turbine. However, in order that the input torque from the impeller is amplified, the stator must be prevented from reverse rotation. On the other hand, during high speed operation, it is desirable to couple the impeller directly to the turbine through a lock-up disc clutch. In this mode, commonly referred to as converter lock-up, it is necessary for the stator to rotate with the impeller and the turbine and in the same direction as the impeller and the turbine. Accordingly, it has been common practice to couple the stator to the converter housing through a roller ramp one-way clutch which prevents the stator from rotating backwards, but allows the stator to rotate with the impeller and the turbine during converter lock-up.

#The invention will now be described, by way of example only, with reference to the drawings, in which:

#FIG. 1 is an axial cross-sectional view of a prior art power transfer device for amplifying engine torque;

#FIGS. 2a-2c are magnified axial cross-sectional views of a power transfer device according to a first embodiment of the invention;

#To assist in the understanding of a first embodiment of the invention, a prior art torque converter power transfer device will be described first, followed by a description of the first embodiment. Turning to FIG. 1, a prior art torque converter power transfer device, denoted generally as 10, is shown comprising a tubular stationary housing 12, an impeller 14 disposed around the housing 12, a turbine 16, and a stator 18 in fluid communication with the impeller 14 and the turbine 16. The impeller 14 includes an input flange 20 and lug nuts 22 for coupling the impeller 14 to torque input means, such as an engine bell housing (not shown), and is rotatably coupled to the housing 12 through a bearing 24 disposed around the housing 12.

#The housing 12 also includes a coaxial rotating output shaft 26 extending through the housing 12. The turbine 16 is coupled to the output shaft 26 through splines 28 provided on the output shaft26. A disc lock-up clutch 30 is provided between the impeller 14 and the turbine 16 for coupling the impeller 14 to the turbine 16 during converter lock-up.

#The stator 18 is coupled to the housing 12 through a roller-ramp one-way clutch 32 which allows the stator 18 to rotate with the impeller 14 and the turbine 16 when lock-up clutch 30 is engaged. When lock-up clutch 30 is disengaged, the one-way clutch 32 prevents the stator 18 from rotating away from the impeller 16. As a consequence, when hydraulic fluid is impelled at the stator 18 from the impeller 14, the input torque applied to the impeller 14 is magnified and transmitted to the turbine 16 for delivery to the output shaft 26.