1. Field of the Invention
The present invention relates to a fluid torque converter for vehicles such as automobiles, which have a built-in on-off type clutch for connecting and disconnecting a pump wheel and a turbine wheel and effecting the mechanical transmission of power from an engine output shaft to a turbine shaft.
2. Description of the Prior Art
A fluid torque converter has been proposed wherein the torque converter comprised a drive plate connected to an engine output shaft, a pump wheel connected to the drive plate, a turbine wheel connected to a turbine shaft provided between the drive plate and the pump wheel, and a one-way, on-off clutch for the mechanical transmission of power from the engine output shaft to the turbine shaft (U.S. patent application Ser. No. 318,985, filed Nov. 6, 1981). Generally, a friction clutch has been used as the direct-coupling clutch for a fluid torque converter. There are, however, advantages when a one-way clutch is used for the direct coupling clutch instead of the friction clutch. That is, when a vehicle is decelerated suddenly, slippage of the one-way clutch occurs and the mechanical transmission of a reverse load from the turbine shaft to the engine shaft via the one-way clutch is automatically cut-off and is shifted to a fluid transmission operation, thus absorbing the reverse load to alleviate the shock which occurs during the sudden deceleration and to achieve better fuel consumption of the vehicle by preventing the engine from an over-revolution which occurs with the mechanical transmission of the reverse load. However, there are some disadvantages in the above-described fluid torque converter which has the one-way clutch built in an inner core of the torque converter defined by and between the pump wheel and the turbine wheels. Specifically, difficulty is encountered in providing the one-way clutch in a fluid torque converter having an oval or elliptical shape in the cross-section of the wheels thereof since the fluid torque converter has a smaller inner core area than a conventional fluid torque converter. Further, a complicated structure in the fluid torque converter is required for an oil passage connected to the one-way clutch since the oil passage must pass through the pump or turbine wheel. Still further, there is little space for designing the one-way clutch since the one-way clutch is provided in the inner core and, therefore, the diameter and the capacity for transmission of power are limited in size and an arrangement of the inner core of the fluid torque converter.